Convert to setup.cfg

[kfdm]

Recent versions of setuptools can run most things from setup.cfg so one can have a simpler version that does not require executing code on install.

The bulk of the changes were automated by running https://pypi.org/project/setup-py-upgrade/ with a few minor edits for the bits that it can not auto convert (the initial get_long_description() and get_version() can not be automatically converted)