[3.13] gh-121592: Make select.poll() and related objects thread-safe (GH-121594) (#121623)

This makes select.poll() and kqueue() objects thread-safe in the
free-threaded build. Note that calling close() concurrently with other
functions is still not thread-safe due to races on file descriptors
(gh-121544).
(cherry picked from commit 44937d11a6a045a624918db78aa36e715ffabcd4)

Co-authored-by: Sam Gross <colesbury@gmail.com>