[3.13] gh-126688: Reinit import lock after fork (GH-126692) (GH-126765)

The PyMutex implementation supports unlocking after fork because we
clear the list of waiters in parking_lot.c. This doesn't work as well
for _PyRecursiveMutex because on some systems, such as SerenityOS, the
thread id is not preserved across fork().
(cherry picked from commit 5610860840aa71b186fc5639211dd268b817d65f)

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