ENH: Implement multi-column `DataFrame.quantiles`
Rough attempt at implementing cuDF's `DataFrame.quantiles`; shares a lot of common logic with `sort_values`, as the indexer that sorts the dataframe by all columns is ultimately what is used to grab the desired quantiles.

cc @quasiben @rjzamora

- [ ] closes #43881
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them
- [ ] whatsnew entry
