BUG: Inconsistent types for groupby group names when grouping with a length-1 list
xref #58858
fixed bug in groupby group names when grouping with a length-1 list
in this PR I changed group `keys` type to `1-tuples` when grouping with a `length-1` list for consistency with the type of group `names`.

To fix the inconsistency with the types, I added the parameter `key_dtype_str` in the `Grouping` constructor. However, these changes have caused some tests to fail, such as: `pandas/tests/groupby/test_grouping.py -k test_groups`

I think my changes should not break existing tests. @rhshadrach, could you please take a look at my changes?
 > However, these changes have caused some tests to fail, such as: `pandas/tests/groupby/test_grouping.py -k test_groups`

This test is checking the behavior that you're changing, the test needs to be updated to the new behavior. In any case, I think this needs to be deprecated before this change can be made. 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.