bpo-42540: reallocation of id_mutex should not force default allocator (GH-29564)


Unlike the other locks reinitialized by _PyRuntimeState_ReInitThreads,
the "interpreters.main->id_mutex" is not freed by _PyRuntimeState_Fini
and should not force the default raw allocator.
(cherry picked from commit 736684b1bb67369a2e95a9f621752deead44e7ef)

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