Since man pages aren't accessible to users after a `pip install`, there's no need to include them in the sdist.
This change makes it trivial to build man pages from source, which makes them much easier to iterate on.
It also simplifies creation and testing of the sdist, since it no longer requires building man pages.
The new `packaging/cli-doc/build.py` script can generate both man pages and RST documentation.
This supports inclusion on the docs site without a dependency on `ansible-core` internals.
Having a single implementation for both simplifies keeping the two formats in sync.
