[3.7] bpo-36533: Reinit logging.Handler locks on fork(). (GH-12704) (GH-13170)

[3.7] bpo-36533: Reinit logging.Handler locks on fork(). (GH-12704) (GH-13170)

Instead of attempting to acquire and release them all across fork
which was leading to deadlocks in some applications that had chained
their own handlers while holding multiple locks.
(cherry picked from commit 64aa6d2000665efb1a2eccae176df9520bf5f5e6)

Co-authored-by: Gregory P. Smith <greg@krypto.org>  [Google LLC]