[3.10] bpo-45021: Fix a hang in forked children (GH-28007) (GH-28480)



_global_shutdown_lock should be reinitialized in forked children
(cherry picked from commit 0bfa1106acfcddc03590e1f5d6789dbad3affe70)


Co-authored-by: nullptr <3621629+0x0L@users.noreply.github.com>

Automerge-Triggered-By: GH:gpshead
3 files changed