ENH: new .agg for list-likes
Part of #43678

- [x] tests added / passed
- [x] 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

Replaces the list-like implementation for `.agg` used by Series, DataFrame, SeriesGroupBy, DataFrameGroupBy, Window, and Resample. This will transpose agg results, and swap multiindex levels as well as the order from within the levels. Adds the new implementation behind the option "new_udf_methods".

Docs: [future_udf_behavior.zip](https://github.com/pandas-dev/pandas/files/7368201/future_udf_behavior.zip)
