[3.9] bpo-37741: make importlib.metadata docs discoverable through a module...

[3.9] bpo-37741: make importlib.metadata docs discoverable through a module directive. (GH-25415) (GH-26500)

Automerge-Triggered-By: GH:jaraco.
(cherry picked from commit 23acadcc)

Co-authored-by: Jason R. Coombs <jaraco@jaraco.com>