[3.11] gh-96522: Fix deadlock in pty.spawn (GH-96639) (#104655)

(cherry picked from commit 9c5aa8967bd7c1b02fb1da055c6b3afcccbbb251)

Co-authored-by: Youfu Zhang <1315097+zhangyoufu@users.noreply.github.com>
4 files changed