BUG: fix AttributeError raised with pd.concat between a None and timezone-aware Timestamp
Take over #53042. I updated the test. It should produce a FutureWarning.

- [x] closes #52093 (Replace xxxx with the GitHub issue number)
- [x] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [x] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.
I notice something weird in the test for reindex with fill_value below.
https://github.com/pandas-dev/pandas/blob/14a6c9ac6873c8afe519a8b47481a12f2f66c5d2/pandas/tests/frame/methods/test_reindex.py#L139-L148
Though the test passes, the representation seems weird. `print(res)` shows,
```console
   0                                   1
0  1 1969-12-31 16:00:01.681173120-08:00
```
while it should be as `print(expected)`:
```console
   0                         1
0  1 2023-04-10 17:32:00-07:00
```
It seems `DatetimeArray` only works when unit is 'ns'. Could you have a further look? @jbrockmendel 
https://github.com/pandas-dev/pandas/blob/14a6c9ac6873c8afe519a8b47481a12f2f66c5d2/pandas/core/internals/managers.py#L2298-L2302 This pull request is stale because it has been open for thirty days with no activity. Please [update](https://pandas.pydata.org/pandas-docs/stable/development/contributing.html#updating-your-pull-request) and respond to this comment if you're still interested in working on this. Thanks for the pull request, but it appears to have gone stale. If interested in continuing, please merge in the main branch, address any review comments and/or failing tests, and we can reopen. Still waiting for requested review, any update needed from my side? This looks good to me.  can you move the whatsnew note to 2.2 > This looks good to me. can you move the whatsnew note to 2.2

Thanks. I've moved the note. Thanks @yuanx749 