Make DTA/TDA/PA return NotImplemented on comparisons
Before implementing a boilerplate decorator like in #24282, going through to standardize the affected behaviors.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24643?src=pr&el=h1) Report
> Merging [#24643](https://codecov.io/gh/pandas-dev/pandas/pull/24643?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/d106e9975100cd0f2080d7b1a6111f20fb64f906?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `90%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24643/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24643?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24643      +/-   ##
==========================================
- Coverage   92.37%   92.37%   -0.01%     
==========================================
  Files         166      166              
  Lines       52379    52382       +3     
==========================================
+ Hits        48386    48387       +1     
- Misses       3993     3995       +2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.79% <90%> (-0.01%)` | :arrow_down: |
| #single | `43.02% <50%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24643?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/arrays/period.py](https://codecov.io/gh/pandas-dev/pandas/pull/24643/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3BlcmlvZC5weQ==) | `98.52% <100%> (-0.02%)` | :arrow_down: |
| [pandas/core/arrays/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/24643/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lcy5weQ==) | `97.69% <100%> (-0.16%)` | :arrow_down: |
| [pandas/core/indexes/datetimelike.py](https://codecov.io/gh/pandas-dev/pandas/pull/24643/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZWxpa2UucHk=) | `98.52% <100%> (ø)` | :arrow_up: |
| [pandas/core/arrays/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/24643/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3RpbWVkZWx0YXMucHk=) | `88.03% <50%> (-0.15%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24643?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/24643?src=pr&el=footer). Last update [d106e99...33cdf67](https://codecov.io/gh/pandas-dev/pandas/pull/24643?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/24643?src=pr&el=h1) Report
> Merging [#24643](https://codecov.io/gh/pandas-dev/pandas/pull/24643?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/d106e9975100cd0f2080d7b1a6111f20fb64f906?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `92.3%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24643/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24643?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24643      +/-   ##
==========================================
- Coverage   92.37%   92.37%   -0.01%     
==========================================
  Files         166      166              
  Lines       52379    52383       +4     
==========================================
+ Hits        48386    48388       +2     
- Misses       3993     3995       +2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.79% <92.3%> (-0.01%)` | :arrow_down: |
| #single | `43.02% <61.53%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24643?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/arrays/period.py](https://codecov.io/gh/pandas-dev/pandas/pull/24643/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3BlcmlvZC5weQ==) | `98.52% <100%> (-0.02%)` | :arrow_down: |
| [pandas/core/arrays/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/24643/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lcy5weQ==) | `97.69% <100%> (-0.16%)` | :arrow_down: |
| [pandas/core/indexes/datetimelike.py](https://codecov.io/gh/pandas-dev/pandas/pull/24643/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZWxpa2UucHk=) | `98.52% <100%> (+0.01%)` | :arrow_up: |
| [pandas/core/arrays/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/24643/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3RpbWVkZWx0YXMucHk=) | `88.03% <50%> (-0.15%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24643?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/24643?src=pr&el=footer). Last update [d106e99...b69c2cb](https://codecov.io/gh/pandas-dev/pandas/pull/24643?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 lgtm ping on green. ping thanks!