[3.12] gh-119960: Add information about regex flags in re module functions (GH-119978) (#120908)

gh-119960: Add information about regex flags in re module functions (#119978)

(cherry picked from commit a86e6255c371e14cab8680dee979a7393b339ce5)

Co-authored-by: Awbert <119314310+SweetyAngel@users.noreply.github.com>