BUG: `pd.core.dtypes.common.is_extension_array_dtype` wrong output for some dtypes
- [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.

- [X] (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

```python
from pandas.core.dtypes.common import is_extension_array_dtype
from pandas.core.base import ExtensionArray

dt = DatetimeArray(np.array([], dtype='datetime64[ns]'))
assert isinstance(dt, ExtensionArray) # passes
assert is_extension_array_dtype(dt) # fails
assert is_extension_array_dtype(dt.dtype) # fails

inter = pd.Interval(0, 5)
assert com.is_extension_array_dtype(inter) # fails
```
Similar problems for `Period` and `timedelta64[ns]`.
#### Problem description

Some of it (example: DatetimeArray) is due to this commit: https://github.com/pandas-dev/pandas/commit/be6885074de3ac333ab0af3271d45bc4eccb307c#diff-e279f0dcc8af317412f2a0db83d50c2ffedcd0743af7da8545ff272ee6ebe2f3R1529

Where DatetimeArray implements ExtensionArray, but `datetime64[ns]` is a np dtype and doesn't (yet) implement ExtensionDtype.

#### Expected Output

Function should return `true` for all dtypes whose Array implements `ExtensionArray`.

I need this for #40450.

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

<details>

INSTALLED VERSIONS
------------------
commit           : a75152784c17a73627a414319f6c89324cfa2840
python           : 3.8.6.final.0
python-bits      : 64
OS               : Linux
OS-release       : 5.8.0-44-generic
Version          : #50-Ubuntu SMP Tue Feb 9 06:29:41 UTC 2021
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : C.UTF-8
LANG             : C.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 1.3.0.dev0+1084.ga75152784c.dirty
numpy            : 1.19.5
pytz             : 2021.1
dateutil         : 2.8.1
pip              : 20.3.3
setuptools       : 49.6.0.post20201009
Cython           : 0.29.22
pytest           : 6.2.2
hypothesis       : 6.7.0
sphinx           : 3.5.2
blosc            : None
feather          : None
xlsxwriter       : 1.3.7
lxml.etree       : 4.6.2
html5lib         : 1.1
pymysql          : None
psycopg2         : None
jinja2           : 2.11.3
IPython          : 7.21.0
pandas_datareader: None
bs4              : 4.9.3
bottleneck       : 1.3.2
fsspec           : 0.8.7
fastparquet      : 0.5.0
gcsfs            : 0.7.2
matplotlib       : 3.3.4
numexpr          : 2.7.3
odfpy            : None
openpyxl         : 3.0.6
pandas_gbq       : None
pyarrow          : 3.0.0
pyxlsb           : None
s3fs             : 0.4.2
scipy            : 1.6.0
sqlalchemy       : 1.3.23
tables           : 3.6.1
tabulate         : 0.8.9
xarray           : 0.17.0
xlrd             : 2.0.1
xlwt             : 1.3.0
numba            : 0.52.0

</details>
