PERF: Regressions between 0.20.1 and 0.20.x
I'll add more later, I'm worried my local benchmarks aren't reliable, but I think these ones are real.


## Interpolate

```
       before           after         ratio
     [20baf972]       [eefbaf71]
+        50.6±2ms            1.48s    29.27  frame_methods.Interpolate.time_interpolate
+     1.19±0.01ms       14.9±0.7ms    12.53  frame_methods.Interpolate.time_interpolate_some_good
+      2.45±0.1ms       13.6±0.8ms     5.57  frame_methods.Interpolate.time_interpolate_some_good_infer

SOME BENCHMARKS HAVE CHANGED SIGNIFICANTLY.
```

## groupby

```
       before           after         ratio
     [20baf972]       [98162e04]
+     1.45±0.03ms      2.49±0.04ms     1.72  groupby.groupby_datetimetz.time_groupby_sum
+     2.71±0.03ms      4.53±0.09ms     1.67  groupby.groupby_nth.time_groupby_series_nth_any
+     1.59±0.02ms      2.51±0.04ms     1.58  groupby.groupby_nth.time_groupby_series_nth_none
+     3.69±0.03ms      4.95±0.09ms     1.34  groupby.groupby_multi.time_groupby_series_simple_cython
+     1.41±0.04ms      1.69±0.04ms     1.19  groupby.groupby_datetime.time_groupby_sum
+     1.91±0.03ms      2.20±0.01ms     1.15  groupby.GroupBySuite.time_cumprod('int', 10000)
+     1.61±0.03ms      1.80±0.02ms     1.12  groupby.GroupBySuite.time_count('int', 10000)
+      9.83±0.2ms      10.9±0.09ms     1.11  groupby.GroupBySuite.time_all('int', 100)
+     1.74±0.03ms      1.93±0.02ms     1.11  groupby.GroupBySuite.time_cummin('int', 10000)
```