A bunch of tiny jobs that run various source or documentation checks are
consolidated into two workflow files: checksrc.yml and checkdocs.yml.
This reduces the proliferation of new files containing one-line checks
and brings those that operate similarly together for better reasoning
about them. The man-examples check is also now running again for the
first time in 7 months.
Various calls to find, xargs and git ls-files are changed where possible
to use NUL line terminators in pipes to avoid issues with oddly-named
files that might find their way into the repo.
Closes#14654