BUG: .dt.isocalendar().week results in the last day of the year as week 1
- [x] I have checked that this issue has not already been reported.

- [x] I have confirmed this bug exists on the latest version of pandas.

- [ ] (optional) I have confirmed this bug exists on the master branch of pandas.

---

**Note**: Please read [this guide](https://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports) detailing how to provide the necessary information for us to reproduce your bug.

#### Code Sample, a copy-pastable example

## Issue 1
```python
import pandas as pd

# sample dataframe
d = pd.DataFrame({'v': [pd.Timestamp('2018-12-03 00:00:00'), pd.Timestamp('2018-12-10 00:00:00'), pd.Timestamp('2018-12-17 00:00:00'), pd.Timestamp('2018-12-24 00:00:00'), pd.Timestamp('2018-12-31 00:00:00')]})

# display(d)
           v
0 2018-12-03
1 2018-12-10
2 2018-12-17
3 2018-12-24
4 2018-12-31

# get the week number
wn = d.v.dt.isocalendar().week

# display(wn)
0    49
1    50
2    51
3    52
4     1
Name: week, dtype: UInt32
```

#### Problem description

- The last day of the week should not be 1, for a given year.
- `d.v.dt.week` also generates the incorrect output, with a 1 
- This is an issue for a number of reasons, but in terms of plotting with week number on the x-axis, the plot line goes from 52, back to 1.

#### Expected Output

- `d.v.dt.strftime('%W').astype(int)` will generate the expected output

```python
0    49
1    50
2    51
3    52
4    53
Name: week, dtype: UInt32
```

## Issue 2:

```python
import pandas as pd

# sample data
data = {'date': pd.bdate_range('2020-11-01', freq='D', periods=93)}
df = pd.DataFrame(data)

# get week number
df['week_strf'] = df.date.dt.strftime('%W').astype('int')
df['week_isocal'] = df.date.dt.isocalendar().week

# display(df.head(10))
        date  week_strf  week_isocal
0 2020-11-01         43           44
1 2020-11-02         44           45
2 2020-11-03         44           45
3 2020-11-04         44           45
4 2020-11-05         44           45
5 2020-11-06         44           45
6 2020-11-07         44           45
7 2020-11-08         44           45
8 2020-11-09         45           46
9 2020-11-10         45           46
```

#### Problem description

- The two methods for getting the week number do not produce the same result

#### Expected Output

- `week_strf` and `week_isocal` should have the same week number

#### Output of ``pd.show_versions()``

<details>

INSTALLED VERSIONS
------------------
commit           : 3e89b4c4b1580aa890023fc550774e63d499da25
python           : 3.8.5.final.0
python-bits      : 64
OS               : Windows
OS-release       : 10
Version          : 10.0.19041
machine          : AMD64
processor        : Intel64 Family 6 Model 60 Stepping 3, GenuineIntel
byteorder        : little
LC_ALL           : None
LANG             : None
LOCALE           : English_United States.1252

pandas           : 1.2.0
numpy            : 1.19.2
pytz             : 2019.3
dateutil         : 2.8.1
pip              : 20.3.3
setuptools       : 51.1.2.post20210110
Cython           : 0.29.21
pytest           : 6.2.1
hypothesis       : None
sphinx           : 3.4.3
blosc            : None
feather          : None
xlsxwriter       : 1.3.7
lxml.etree       : 4.6.2
html5lib         : 1.1
pymysql          : None
psycopg2         : None
jinja2           : 2.11.2
IPython          : 7.19.0
pandas_datareader: 0.9.0
bs4              : 4.9.3
bottleneck       : 1.3.2
fsspec           : 0.8.3
fastparquet      : None
gcsfs            : None
matplotlib       : 3.3.2
numexpr          : 2.7.2
odfpy            : None
openpyxl         : 3.0.5
pandas_gbq       : None
pyarrow          : None
pyxlsb           : None
s3fs             : None
scipy            : 1.5.2
sqlalchemy       : 1.3.21
tables           : 3.6.1
tabulate         : 0.8.7
xarray           : None
xlrd             : 2.0.1
xlwt             : 1.3.0
numba            : 0.51.2

</details>
