[3.14] gh-144169: Fix three crashes in AST objects with non-str kwargs (GH-144178) (#144227)

gh-144169: Fix three crashes in AST objects with non-str kwargs (GH-144178)
(cherry picked from commit 639c1ad4f1ef5c2409a62fa8ed16e6aa3a6f9ab8)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Co-authored-by: Victor Stinner <vstinner@python.org>