Clean unnecessary lock of WindowAnimator#animate

Reduce the invocation of thread priority booster and
monitor-enter/exit.

- The prohibition of lock was introduced in commits
  9b19fd42 and 836dac49, but since commit 32fd84ac that
  enabled lock free app animations on surface animation
  thread, the original WindowAnimator#animate is safe
  to be put in WM global lock.
- All invocations of open/closeSurfaceTransaction are
  inside WM global lock.

Bug: 139522754
Test: atest WindowTest
Change-Id: Idb11b4e5bc3b982341d86cad33f6c23253d0d0d9