Fix the CC monkey crashes.

Add ScopedGCCriticalSection around the monitor deflation to avoid race
conditions on the lock word.

Bug: 31773180
Bug: 31712602
Bug: 31712174
Bug: 31712601
Bug: 31712256
Bug: 31710993
Bug: 12687968
Test: test-art host/N9, N9 libartd boot, Ritz EAAC.
Change-Id: Id05c6502fb08ca2e0770af4940b737038c3412d6