[3.12] gh-102211: Document `re.{Pattern,Match}`’s existence (GH-102212) (#108490)

gh-102211: Document `re.{Pattern,Match}`’s existence (GH-102212)
(cherry picked from commit 6895ddf6cb2bada7e392eb971c88ded03d8fc79e)

Co-authored-by: Philipp A <flying-sheep@web.de>
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>