COMPAT: properly handle objects of datetimelike in astype_nansafe
re-close #19116

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19232?src=pr&el=h1) Report
> Merging [#19232](https://codecov.io/gh/pandas-dev/pandas/pull/19232?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/04778805dd595e37e33f6ef0e02d9337a1154e09?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `84.61%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/19232/graphs/tree.svg?src=pr&width=650&token=eZ4WkYLtcO&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/19232?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #19232      +/-   ##
==========================================
- Coverage   91.55%   91.54%   -0.01%     
==========================================
  Files         147      147              
  Lines       48797    48804       +7     
==========================================
+ Hits        44675    44680       +5     
- Misses       4122     4124       +2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.92% <84.61%> (-0.01%)` | :arrow_down: |
| #single | `41.61% <61.53%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/19232?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/dtypes/cast.py](https://codecov.io/gh/pandas-dev/pandas/pull/19232/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2Nhc3QucHk=) | `88.15% <84.61%> (-0.21%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19232?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19232?src=pr&el=footer). Last update [0477880...cc1ded7](https://codecov.io/gh/pandas-dev/pandas/pull/19232?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
