[3.12] gh-94220: Align fnmatch docs with the implementation and amend markup (GH-114152) (#114155)

- Align the argument spec for fnmatch functions with the actual
  implementation.
- Update Sphinx markup to recent recommandations.
- Add link to 'iterable' glossary entry.

(cherry picked from commit 6e84f3b56f445b56ab48723d636c0a17090298ab)

Co-authored-by: Erlend E. Aasland <erlend@python.org>
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>