CLN: ASV offset
- Consolidated all the offsets to a list that was reused for all the benchmarks.

- The `ApplyIndex` benchmark seemed to be benchmarking arithmetic, so I changed it to specifically use the `apply_index()` method

```
$ asv dev -b ^offset
· Discovering benchmarks
· Running 10 total benchmarks (1 commits * 1 environments * 10 benchmarks)
[  0.00%] ·· Building for existing-py_home_matt_anaconda_envs_pandas_dev_bin_python
[  0.00%] ·· Benchmarking existing-py_home_matt_anaconda_envs_pandas_dev_bin_python
[ 10.00%] ··· Running offset.ApplyIndex.time_apply_index                              ok
[ 10.00%] ···· 
               ============================================= ========
                                   offset                            
               --------------------------------------------- --------
                            <YearEnd: month=12>               173ms  
                            <YearBegin: month=1>              6.94ms 
                       <QuarterEnd: startingMonth=3>          194ms  
                      <QuarterBegin: startingMonth=3>         7.15ms 
                                 <MonthEnd>                   1.28ms 
                                <MonthBegin>                  1.19ms 
                <DateOffset: kwds={'months': 2, 'days': 2}>   2.45ms 
                               <BusinessDay>                  136ms  
                      <SemiMonthEnd: day_of_month=15>         138ms  
                     <SemiMonthBegin: day_of_month=15>        140ms  
               ============================================= ========

[ 20.00%] ··· Running offset.OffestDatetimeArithmetic.time_add                        ok
[ 20.00%] ···· 
               ============================================= ========
                                   offset                            
               --------------------------------------------- --------
                                   <Day>                      106μs  
                        <BusinessYearEnd: month=12>           202μs  
                        <BusinessYearBegin: month=1>          123μs  
                   <BusinessQuarterEnd: startingMonth=3>      105μs  
                  <BusinessQuarterBegin: startingMonth=3>     124μs  
                             <BusinessMonthEnd>               121μs  
                            <BusinessMonthBegin>              138μs  
                            <CustomBusinessDay>               89.2μs 
                            <CustomBusinessDay>               89.6μs 
                         <CustomBusinessMonthBegin>           415μs  
                          <CustomBusinessMonthEnd>            442μs  
                          <CustomBusinessMonthEnd>            422μs  
                            <YearEnd: month=12>               63.0μs 
                            <YearBegin: month=1>              61.7μs 
                       <QuarterEnd: startingMonth=3>          105μs  
                      <QuarterBegin: startingMonth=3>         150μs  
                                 <MonthEnd>                   176μs  
                                <MonthBegin>                  121μs  
                <DateOffset: kwds={'months': 2, 'days': 2}>   69.2μs 
                               <BusinessDay>                  84.9μs 
                      <SemiMonthEnd: day_of_month=15>         179μs  
                     <SemiMonthBegin: day_of_month=15>        177μs  
               ============================================= ========

[ 30.00%] ··· Running offset.OffestDatetimeArithmetic.time_add_10                     ok
[ 30.00%] ···· 
               ============================================= ========
                                   offset                            
               --------------------------------------------- --------
                                   <Day>                      121μs  
                        <BusinessYearEnd: month=12>           161μs  
                        <BusinessYearBegin: month=1>          162μs  
                   <BusinessQuarterEnd: startingMonth=3>      207μs  
                  <BusinessQuarterBegin: startingMonth=3>     137μs  
                             <BusinessMonthEnd>               141μs  
                            <BusinessMonthBegin>              156μs  
                            <CustomBusinessDay>               111μs  
                            <CustomBusinessDay>               121μs  
                         <CustomBusinessMonthBegin>           458μs  
                          <CustomBusinessMonthEnd>            464μs  
                          <CustomBusinessMonthEnd>            461μs  
                            <YearEnd: month=12>               129μs  
                            <YearBegin: month=1>              99.1μs 
                       <QuarterEnd: startingMonth=3>          115μs  
                      <QuarterBegin: startingMonth=3>         219μs  
                                 <MonthEnd>                   192μs  
                                <MonthBegin>                  148μs  
                <DateOffset: kwds={'months': 2, 'days': 2}>   280μs  
                               <BusinessDay>                  101μs  
                      <SemiMonthEnd: day_of_month=15>         187μs  
                     <SemiMonthBegin: day_of_month=15>        185μs  
               ============================================= ========

[ 40.00%] ··· Running offset.OffestDatetimeArithmetic.time_apply                      ok
[ 40.00%] ···· 
               ============================================= ========
                                   offset                            
               --------------------------------------------- --------
                                   <Day>                      98.1μs 
                        <BusinessYearEnd: month=12>           192μs  
                        <BusinessYearBegin: month=1>          116μs  
                   <BusinessQuarterEnd: startingMonth=3>      96.5μs 
                  <BusinessQuarterBegin: startingMonth=3>     116μs  
                             <BusinessMonthEnd>               118μs  
                            <BusinessMonthBegin>              129μs  
                            <CustomBusinessDay>               79.8μs 
                            <CustomBusinessDay>               81.3μs 
                         <CustomBusinessMonthBegin>           526μs  
                          <CustomBusinessMonthEnd>            416μs  
                          <CustomBusinessMonthEnd>            414μs  
                            <YearEnd: month=12>               53.1μs 
                            <YearBegin: month=1>              51.8μs 
                       <QuarterEnd: startingMonth=3>          95.0μs 
                      <QuarterBegin: startingMonth=3>         137μs  
                                 <MonthEnd>                   165μs  
                                <MonthBegin>                  113μs  
                <DateOffset: kwds={'months': 2, 'days': 2}>   61.1μs 
                               <BusinessDay>                  76.8μs 
                      <SemiMonthEnd: day_of_month=15>         170μs  
                     <SemiMonthBegin: day_of_month=15>        168μs  
               ============================================= ========

[ 50.00%] ··· Running offset.OffestDatetimeArithmetic.time_apply_np_dt64              ok
[ 50.00%] ···· 
               ============================================= ========
                                   offset                            
               --------------------------------------------- --------
                                   <Day>                      104μs  
                        <BusinessYearEnd: month=12>           199μs  
                        <BusinessYearBegin: month=1>          121μs  
                   <BusinessQuarterEnd: startingMonth=3>      105μs  
                  <BusinessQuarterBegin: startingMonth=3>     123μs  
                             <BusinessMonthEnd>               121μs  
                            <BusinessMonthBegin>              137μs  
                            <CustomBusinessDay>               86.2μs 
                            <CustomBusinessDay>               88.0μs 
                         <CustomBusinessMonthBegin>           411μs  
                          <CustomBusinessMonthEnd>            420μs  
                          <CustomBusinessMonthEnd>            421μs  
                            <YearEnd: month=12>               60.4μs 
                            <YearBegin: month=1>              58.5μs 
                       <QuarterEnd: startingMonth=3>          103μs  
                      <QuarterBegin: startingMonth=3>         119μs  
                                 <MonthEnd>                   174μs  
                                <MonthBegin>                  118μs  
                <DateOffset: kwds={'months': 2, 'days': 2}>   69.0μs 
                               <BusinessDay>                  82.6μs 
                      <SemiMonthEnd: day_of_month=15>         178μs  
                     <SemiMonthBegin: day_of_month=15>        173μs  
               ============================================= ========

[ 60.00%] ··· Running offset.OffestDatetimeArithmetic.time_subtract                   ok
[ 60.00%] ···· 
               ============================================= ========
                                   offset                            
               --------------------------------------------- --------
                                   <Day>                      125μs  
                        <BusinessYearEnd: month=12>           165μs  
                        <BusinessYearBegin: month=1>          165μs  
                   <BusinessQuarterEnd: startingMonth=3>      117μs  
                  <BusinessQuarterBegin: startingMonth=3>     136μs  
                             <BusinessMonthEnd>               145μs  
                            <BusinessMonthBegin>              144μs  
                            <CustomBusinessDay>               114μs  
                            <CustomBusinessDay>               105μs  
                         <CustomBusinessMonthBegin>           380μs  
                          <CustomBusinessMonthEnd>            564μs  
                          <CustomBusinessMonthEnd>            569μs  
                            <YearEnd: month=12>               104μs  
                            <YearBegin: month=1>              104μs  
                       <QuarterEnd: startingMonth=3>          114μs  
                      <QuarterBegin: startingMonth=3>         130μs  
                                 <MonthEnd>                   209μs  
                                <MonthBegin>                  140μs  
                <DateOffset: kwds={'months': 2, 'days': 2}>   129μs  
                               <BusinessDay>                  85.2μs 
                      <SemiMonthEnd: day_of_month=15>         191μs  
                     <SemiMonthBegin: day_of_month=15>        188μs  
               ============================================= ========

[ 70.00%] ··· Running offset.OffestDatetimeArithmetic.time_subtract_10                ok
[ 70.00%] ···· 
               ============================================= =======
                                   offset                           
               --------------------------------------------- -------
                                   <Day>                      139μs 
                        <BusinessYearEnd: month=12>           198μs 
                        <BusinessYearBegin: month=1>          196μs 
                   <BusinessQuarterEnd: startingMonth=3>      126μs 
                  <BusinessQuarterBegin: startingMonth=3>     146μs 
                             <BusinessMonthEnd>               157μs 
                            <BusinessMonthBegin>              158μs 
                            <CustomBusinessDay>               144μs 
                            <CustomBusinessDay>               114μs 
                         <CustomBusinessMonthBegin>           386μs 
                          <CustomBusinessMonthEnd>            482μs 
                          <CustomBusinessMonthEnd>            478μs 
                            <YearEnd: month=12>               156μs 
                            <YearBegin: month=1>              136μs 
                       <QuarterEnd: startingMonth=3>          123μs 
                      <QuarterBegin: startingMonth=3>         140μs 
                                 <MonthEnd>                   210μs 
                                <MonthBegin>                  154μs 
                <DateOffset: kwds={'months': 2, 'days': 2}>   516μs 
                               <BusinessDay>                  115μs 
                      <SemiMonthEnd: day_of_month=15>         197μs 
                     <SemiMonthBegin: day_of_month=15>        195μs 
               ============================================= =======

[ 80.00%] ··· Running offset.OffsetDatetimeIndexArithmetic.time_add_offset            ok
[ 80.00%] ···· 
               ============================================= ========
                                   offset                            
               --------------------------------------------- --------
                                   <Day>                      1.14ms 
                        <BusinessYearEnd: month=12>           1.97s  
                        <BusinessYearBegin: month=1>          1.08s  
                   <BusinessQuarterEnd: startingMonth=3>      920ms  
                  <BusinessQuarterBegin: startingMonth=3>     1.10s  
                             <BusinessMonthEnd>               1.07s  
                            <BusinessMonthBegin>              1.14s  
                            <CustomBusinessDay>               752ms  
                            <CustomBusinessDay>               754ms  
                         <CustomBusinessMonthBegin>           4.56s  
                          <CustomBusinessMonthEnd>            4.04s  
                          <CustomBusinessMonthEnd>            4.02s  
                            <YearEnd: month=12>               172ms  
                            <YearBegin: month=1>              7.10ms 
                       <QuarterEnd: startingMonth=3>          191ms  
                      <QuarterBegin: startingMonth=3>         7.13ms 
                                 <MonthEnd>                   1.48ms 
                                <MonthBegin>                  1.40ms 
                <DateOffset: kwds={'months': 2, 'days': 2}>   3.09ms 
                               <BusinessDay>                  137ms  
                      <SemiMonthEnd: day_of_month=15>         141ms  
                     <SemiMonthBegin: day_of_month=15>        136ms  
               ============================================= ========

[ 90.00%] ··· Running offset.OffsetSeriesArithmetic.time_add_offset                   ok
[ 90.00%] ···· 
               ============================================= =======
                                   offset                           
               --------------------------------------------- -------
                                   <Day>                      416ms 
                        <BusinessYearEnd: month=12>           2.39s 
                        <BusinessYearBegin: month=1>          1.50s 
                   <BusinessQuarterEnd: startingMonth=3>      1.34s 
                  <BusinessQuarterBegin: startingMonth=3>     1.51s 
                             <BusinessMonthEnd>               1.49s 
                            <BusinessMonthBegin>              1.56s 
                            <CustomBusinessDay>               1.17s 
                            <CustomBusinessDay>               1.18s 
                         <CustomBusinessMonthBegin>           5.02s 
                          <CustomBusinessMonthEnd>            4.49s 
                          <CustomBusinessMonthEnd>            4.46s 
                            <YearEnd: month=12>               588ms 
                            <YearBegin: month=1>              426ms 
                       <QuarterEnd: startingMonth=3>          611ms 
                      <QuarterBegin: startingMonth=3>         425ms 
                                 <MonthEnd>                   422ms 
                                <MonthBegin>                  420ms 
                <DateOffset: kwds={'months': 2, 'days': 2}>   422ms 
                               <BusinessDay>                  549ms 
                      <SemiMonthEnd: day_of_month=15>         559ms 
                     <SemiMonthBegin: day_of_month=15>        561ms 
               ============================================= =======

[100.00%] ··· Running offset.OnOffset.time_on_offset                                  ok
[100.00%] ···· 
               ============================================= ========
                                   offset                            
               --------------------------------------------- --------
                                   <Day>                      28.1μs 
                        <BusinessYearEnd: month=12>           6.93ms 
                        <BusinessYearBegin: month=1>          5.21ms 
                   <BusinessQuarterEnd: startingMonth=3>      5.61ms 
                  <BusinessQuarterBegin: startingMonth=3>     4.61ms 
                             <BusinessMonthEnd>               5.33ms 
                            <BusinessMonthBegin>              34.6μs 
                            <CustomBusinessDay>               409μs  
                            <CustomBusinessDay>               408μs  
                         <CustomBusinessMonthBegin>           16.1ms 
                          <CustomBusinessMonthEnd>            16.3ms 
                          <CustomBusinessMonthEnd>            16.3ms 
                            <YearEnd: month=12>               34.7μs 
                            <YearBegin: month=1>              21.3μs 
                       <QuarterEnd: startingMonth=3>          252μs  
                      <QuarterBegin: startingMonth=3>         4.48ms 
                                 <MonthEnd>                   34.5μs 
                                <MonthBegin>                  18.8μs 
                <DateOffset: kwds={'months': 2, 'days': 2}>   21.4μs 
                               <BusinessDay>                  21.0μs 
                      <SemiMonthEnd: day_of_month=15>         38.6μs 
                     <SemiMonthBegin: day_of_month=15>        22.6μs 
               ============================================= ========
``` 