REF: extract more functions in pandas/core/describe.py
- [ ] xref #36833
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry

Extracted ``describe_series``, ``describe_frame`` and ``select_column`` in ``pandas/core/describe.py``.
The next time I think I will introduce the classes ``SeriesDescriber`` and ``DataFrameDescriber`` and will start moving the functions into the methods incrementally, if that is OK.