Merge branch '2023-02-07-Kconfig-cleanup-dead-code-removal'

To quote the author:
This series adds source scanning to moveconfig.py so that it can look
for Kconfig options mentioned in the source which do not appear in
Kconfig, and vice versa.

This tool is then used to clean up the unused or obsolete options
mentioned in Makefiles, along with any attached source code.