ENH: Add numeric_only to certain groupby ops
Part of #46560

- [x] Closes #46524  
- [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 an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

For the ops that have numeric_only added, we have the option of dropping nuisance columns even when `numeric_only=False` is specified to be consistent with other groupby ops (e.g. sum). I decided to implement the correct behavior here instead; this required adding an argument to the cython/python paths. This argument can be removed in 2.0 when all ops would raise.
@jreback - gentle ping. thanks @rhshadrach very nice!
