DEPR: Remove Panel-specific parts of io.pytables
Is it the case that LegacyTable and AppendableTable are never used directly, only their subclasses?  If so, some further simplifications are available.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25233?src=pr&el=h1) Report
> Merging [#25233](https://codecov.io/gh/pandas-dev/pandas/pull/25233?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/1d1b14c7ea7c3e497b66453cacbb8230b26cb6a6?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/25233/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25233?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25233      +/-   ##
==========================================
- Coverage   92.15%   92.15%   -0.01%     
==========================================
  Files         166      166              
  Lines       52294    52234      -60     
==========================================
- Hits        48194    48136      -58     
+ Misses       4100     4098       -2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.69% <100%> (+0.07%)` | :arrow_up: |
| #single | `42.17% <100%> (-0.1%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25233?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/internals/blocks.py](https://codecov.io/gh/pandas-dev/pandas/pull/25233/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2Jsb2Nrcy5weQ==) | `94.1% <ø> (+0.13%)` | :arrow_up: |
| [pandas/core/internals/\_\_init\_\_.py](https://codecov.io/gh/pandas-dev/pandas/pull/25233/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL19faW5pdF9fLnB5) | `100% <ø> (ø)` | :arrow_up: |
| [pandas/io/pytables.py](https://codecov.io/gh/pandas-dev/pandas/pull/25233/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3B5dGFibGVzLnB5) | `90.2% <100%> (-0.23%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25233?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/25233?src=pr&el=footer). Last update [1d1b14c...8e1534a](https://codecov.io/gh/pandas-dev/pandas/pull/25233?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/25233?src=pr&el=h1) Report
> Merging [#25233](https://codecov.io/gh/pandas-dev/pandas/pull/25233?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/1d1b14c7ea7c3e497b66453cacbb8230b26cb6a6?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/25233/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25233?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25233      +/-   ##
==========================================
- Coverage   92.15%   92.15%   -0.01%     
==========================================
  Files         166      166              
  Lines       52294    52234      -60     
==========================================
- Hits        48194    48136      -58     
+ Misses       4100     4098       -2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.69% <100%> (+0.07%)` | :arrow_up: |
| #single | `42.17% <100%> (-0.1%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25233?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/internals/blocks.py](https://codecov.io/gh/pandas-dev/pandas/pull/25233/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2Jsb2Nrcy5weQ==) | `94.1% <ø> (+0.13%)` | :arrow_up: |
| [pandas/core/internals/\_\_init\_\_.py](https://codecov.io/gh/pandas-dev/pandas/pull/25233/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL19faW5pdF9fLnB5) | `100% <ø> (ø)` | :arrow_up: |
| [pandas/io/pytables.py](https://codecov.io/gh/pandas-dev/pandas/pull/25233/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3B5dGFibGVzLnB5) | `90.2% <100%> (-0.23%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25233?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/25233?src=pr&el=footer). Last update [1d1b14c...8e1534a](https://codecov.io/gh/pandas-dev/pandas/pull/25233?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks @jbrockmendel 

> Is it the case that LegacyTable and AppendableTable are never used directly, only their subclasses? If so, some further simplifications are available.

IIRC yes I think so