BUG: Tuple subclasses should work as tuple in `df.iloc[key]`
- Closes #48188
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

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This patch makes tuple subclasses behave the same as tuple in `df.iloc[key]` and `df.loc[key]`.  All but one of the tests pass.  The failing test (`indexing/test_loc.py::TestLocBaseIndependent::test_loc_getitem_index_namedtuple`) raises an exception on `df.loc[key]` (not `.iloc`).  I've opened issue #50597 where I suggest deprecating the behavior in that test.  This patch would enforce that deprecation in addition to closing #48188.

I'm opening this as is WIP but please comment.  I have doubts on whether I'm on the right track with this.

This pull request is stale because it has been open for thirty days with no activity. Please [update](https://pandas.pydata.org/pandas-docs/stable/development/contributing.html#updating-your-pull-request) and respond to this comment if you're still interested in working on this. Thanks for the pull request, but it appears to have gone stale. If interested in continuing, please merge in the main branch, address any review comments and/or failing tests, and we can reopen.