ENH: `assert_frame_equal` to show column name for columns of dtype `datetime64[ns]`
#### Is your feature request related to a problem?

I wish I could use [`pandas.testing.assert_frame_equal`](https://pandas.pydata.org/docs/reference/api/pandas.testing.assert_frame_equal.html) to determine which of my `datetime64[ns]` columns are not equal when comparing two dataframes. Currently the output is `AssertionError: numpy array are different` without indicating which columns are different.

#### Describe the solution you'd like

When two dataframes with `datetime64[ns]` columns are compared using [`pandas.testing.assert_frame_equal`](https://pandas.pydata.org/docs/reference/api/pandas.testing.assert_frame_equal.html) and there are different values, the output should also have the column name that has this difference, e.g. `AssertionError: DataFrame.iloc[:, 1] (column name="b") are different`.

#### Additional context

Minimal reproducible code below. If you change one of the `datetime` values to an integer, the dtype of the column will be `object`, in which case, the desired behaviour is shown.

```python
import pandas as pd
from pandas.testing import assert_frame_equal

df_left = pd.DataFrame({'a': [1, 2], 'b': [
    datetime(2021, 1, 1), 
#     1,
    datetime(2021, 1, 2)
]})
df_right = pd.DataFrame({'a': [1, 2], 'b': [
    datetime(2021, 1, 1), 
#     1,
    datetime(2021, 1, 3)
]})

assert_frame_equal(left=df_left, right=df_right)
```
