TST: MultiIndex.get_indexer with na/missing
- [x] closes #43222
- [x] closes #46173
- [x] closes #42883
- [x] closes #38623
- [x] closes #29252
- [x] closes #48905 
- [x] [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
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [x] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [x] Added an entry in the latest `doc/source/whatsnew/v2.0.0.rst` file if fixing a bug or adding a new feature.


Update: #49442 has been merged to fix the underlying bug here. This PR has been updated to add tests for closing the linked issues which are all related to the same underlying bug in #49442.

Could you rebase? Hopefully, all tests should pass now. Also, would be good to add the issues to my whatsnew note. wdyt? > Could you rebase? Hopefully, all tests should pass now. Also, would be good to add the issues to my whatsnew note. wdyt?

Updated this PR to add tests only and close linked issues. If you think any of these tests are redundant, I'm happy to remove some (all reported for the same underlying bug).