REF: put DatetimeBlock adjacent to DatetimeLikeBlockMixin
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

just a straight move? yep k ping on green # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24582?src=pr&el=h1) Report
> Merging [#24582](https://codecov.io/gh/pandas-dev/pandas/pull/24582?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/4b91140a1068f80c2b6953d8950dbfedde7144c7?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `94.1%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24582/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24582?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24582      +/-   ##
==========================================
+ Coverage   92.36%   92.36%   +<.01%     
==========================================
  Files         166      166              
  Lines       52494    52494              
==========================================
+ Hits        48485    48486       +1     
+ Misses       4009     4008       -1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.79% <94.1%> (ø)` | :arrow_up: |
| #single | `43.04% <43.43%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24582?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/internals/blocks.py](https://codecov.io/gh/pandas-dev/pandas/pull/24582/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2Jsb2Nrcy5weQ==) | `93.79% <94.1%> (+0.06%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24582?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/24582?src=pr&el=footer). Last update [4b91140...e66487e](https://codecov.io/gh/pandas-dev/pandas/pull/24582?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24582?src=pr&el=h1) Report
> Merging [#24582](https://codecov.io/gh/pandas-dev/pandas/pull/24582?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/4b91140a1068f80c2b6953d8950dbfedde7144c7?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `94.1%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24582/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24582?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24582      +/-   ##
==========================================
+ Coverage   92.36%   92.36%   +<.01%     
==========================================
  Files         166      166              
  Lines       52494    52494              
==========================================
+ Hits        48485    48486       +1     
+ Misses       4009     4008       -1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.79% <94.1%> (ø)` | :arrow_up: |
| #single | `43.04% <43.43%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24582?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/internals/blocks.py](https://codecov.io/gh/pandas-dev/pandas/pull/24582/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2Jsb2Nrcy5weQ==) | `93.79% <94.1%> (+0.06%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24582?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/24582?src=pr&el=footer). Last update [4b91140...e66487e](https://codecov.io/gh/pandas-dev/pandas/pull/24582?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 ping