BUG: Date offset on numpy datetime64 does not work for week and month offsets
- [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.

---

#### Code Sample

```python
import numpy as np
import pandas as pd

# test data: a numpy Datetime64
ts_np = np.Datetime64('2021-01-01T08:00:00.00')

# 1 hour offset: works as expected (1 day offset also works as expected)
do=pd.tseries.frequencies.to_offset('1h')
ts_np + do
```
Result
```bash
Timestamp('2021-01-01 09:00:00')
```

```python
# 1 week offset returns an error
do=pd.tseries.frequencies.to_offset('1W')
ts_np + do
```
Result
```bash
ts_np+do
Traceback (most recent call last):

  File "<ipython-input-11-e20c02eb9ea8>", line 1, in <module>
    ts_np+do

UFuncTypeError: ufunc 'add' cannot use operands with types dtype('<M8[ms]') and dtype('O')
```
```python
# 1 month begin offset returns an error
do=pd.tseries.frequencies.to_offset('1MS')
```
Result
```bash
ts_np+do
Traceback (most recent call last):

  File "<ipython-input-13-e20c02eb9ea8>", line 1, in <module>
    ts_np+do

UFuncTypeError: ufunc 'add' cannot use operands with types dtype('<M8[ms]') and dtype('O')
```

#### Problem description
Applying week or month offset on numpy `Datetime64` does not work.

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

<details>

INSTALLED VERSIONS
------------------
commit           : 2cb96529396d93b46abab7bbc73a208e708c642e
python           : 3.8.5.final.0
python-bits      : 64
OS               : Linux
OS-release       : 5.8.0-53-generic
Version          : #60~20.04.1-Ubuntu SMP Thu May 6 09:52:46 UTC 2021
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : fr_FR.UTF-8
LOCALE           : fr_FR.UTF-8

pandas           : 1.2.4
numpy            : 1.20.1
pytz             : 2021.1
dateutil         : 2.8.1
pip              : 21.1.1
setuptools       : 52.0.0.post20210125
Cython           : 0.29.23
pytest           : 6.2.3
hypothesis       : None
sphinx           : 4.0.1
blosc            : None
feather          : None
xlsxwriter       : 1.3.8
lxml.etree       : 4.6.3
html5lib         : 1.1
pymysql          : None
psycopg2         : None
jinja2           : 3.0.0
IPython          : 7.22.0
pandas_datareader: None
bs4              : 4.9.3
bottleneck       : 1.3.2
fsspec           : 0.9.0
fastparquet      : 0.6.0
gcsfs            : None
matplotlib       : 3.3.4
numexpr          : 2.7.3
odfpy            : None
openpyxl         : 3.0.7
pandas_gbq       : None
pyarrow          : 2.0.0
pyxlsb           : None
s3fs             : None
scipy            : 1.6.2
sqlalchemy       : 1.4.15
tables           : 3.6.1
tabulate         : None
xarray           : None
xlrd             : 2.0.1
xlwt             : 1.3.0
numba            : 0.51.2

</details>
