BUG: Assorted DTA/TDA/PI bugfixes
Fixes a problem with tz-aware DatetimeArray.round (ref #24038)
Fixes PI, PA, DTA failing to validate lengths when doing comparisons against length-1 instances (ref #23078)
Pins names to a handful of methods that currently don't have them (working on a separate branch that checks these systematically; these are the low-hanging fruit)

- [x] closes #23078
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24397?src=pr&el=h1) Report
> Merging [#24397](https://codecov.io/gh/pandas-dev/pandas/pull/24397?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/3e0358d869f8a76b3223e8bb313a92edbaa369db?src=pr&el=desc) will **decrease** coverage by `49.31%`.
> The diff coverage is `58.33%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24397/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24397?src=pr&el=tree)

```diff
@@             Coverage Diff             @@
##           master   #24397       +/-   ##
===========================================
- Coverage    92.3%   42.99%   -49.32%     
===========================================
  Files         162      162               
  Lines       51875    51886       +11     
===========================================
- Hits        47883    22308    -25575     
- Misses       3992    29578    +25586
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `?` | |
| #single | `42.99% <58.33%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24397?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/arrays/datetimelike.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lbGlrZS5weQ==) | `48.58% <0%> (-47.94%)` | :arrow_down: |
| [pandas/core/arrays/period.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3BlcmlvZC5weQ==) | `37.95% <0%> (-60.55%)` | :arrow_down: |
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `49.38% <100%> (-44.34%)` | :arrow_down: |
| [pandas/core/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvb3BzLnB5) | `55.64% <100%> (-38.63%)` | :arrow_down: |
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `56.17% <100%> (-40.1%)` | :arrow_down: |
| [pandas/core/arrays/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3RpbWVkZWx0YXMucHk=) | `40.13% <50%> (-47.03%)` | :arrow_down: |
| [pandas/core/arrays/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lcy5weQ==) | `66.37% <50%> (-31.87%)` | :arrow_down: |
| [pandas/io/formats/latex.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvbGF0ZXgucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/core/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY2F0ZWdvcmljYWwucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/sas/sas\_constants.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfY29uc3RhbnRzLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| ... and [127 more](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24397?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/24397?src=pr&el=footer). Last update [3e0358d...dc37dfb](https://codecov.io/gh/pandas-dev/pandas/pull/24397?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/24397?src=pr&el=h1) Report
> Merging [#24397](https://codecov.io/gh/pandas-dev/pandas/pull/24397?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/6b31abdbad403255ec995603daa42ccbffec7543?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24397/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24397?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24397      +/-   ##
==========================================
- Coverage    92.3%    92.3%   -0.01%     
==========================================
  Files         163      163              
  Lines       51946    51958      +12     
==========================================
+ Hits        47949    47959      +10     
- Misses       3997     3999       +2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.71% <100%> (-0.01%)` | :arrow_down: |
| #single | `43% <64.28%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24397?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/arrays/datetimelike.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lbGlrZS5weQ==) | `96.14% <100%> (-0.22%)` | :arrow_down: |
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `93.72% <100%> (ø)` | :arrow_up: |
| [pandas/core/arrays/period.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3BlcmlvZC5weQ==) | `98.48% <100%> (ø)` | :arrow_up: |
| [pandas/core/arrays/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3RpbWVkZWx0YXMucHk=) | `86.91% <100%> (+0.05%)` | :arrow_up: |
| [pandas/core/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvb3BzLnB5) | `94.28% <100%> (+0.02%)` | :arrow_up: |
| [pandas/core/arrays/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2RhdGV0aW1lcy5weQ==) | `97.6% <100%> (-0.18%)` | :arrow_down: |
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/24397/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `96.27% <100%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24397?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/24397?src=pr&el=footer). Last update [6b31abd...fd2b180](https://codecov.io/gh/pandas-dev/pandas/pull/24397?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 is this orthogonal to #23078, should close that one?  > is this orthogonal to #23078, should close that one?

This closes #23078, should be reflected in the OP. i think comments have been addressed thanks. pls followup on the ops name tests at some point.