Don't use WMS.mWindowMap to synchronize WM critical section (36/n)

Use new field WMS.mGlobalLock instead. This will make it easier to
switch the lock to the same object used by ActivityTaskManagerService
in an upcoming CL.

Test: Existing tests pass
Bug: 80414790
Change-Id: I4202e9028395d79cc60b01ed795528b469a16bf1
40 files changed