[3.13] gh-123523: Rework typing documentation for generators and coroutines, and link to it from `collections.abc` docs (GH-123544) (#123790)

gh-123523: Rework typing documentation for generators and coroutines, and link to it from `collections.abc` docs (GH-123544)
(cherry picked from commit 56e4a417ce170e5c538ce9aafccf3333e7bf7492)

Co-authored-by: Stanislav Terliakov <50529348+sterliakov@users.noreply.github.com>