[3.11] gh-68966: Make mailcap refuse to match unsafe filenames/types/params (GH-91993) (GH-93458)

(cherry picked from commit b9509ba7a9c668b984dab876c7926fe1dc5aa0ba)


Co-authored-by: Petr Viktorin <encukou@gmail.com>

Automerge-Triggered-By: GH:encukou