Window Manager spring cleaning

Our performance for wmLayout + prepareSurfaces regressed over
time, because we added a lot of functionality, but didn't have
fine grained perf tests enough to catch it.

This CL tries to attempt to undo that damage by optimizing various
things that regressed or didn't regress, but could still be
optimized.

Test: Presubmit tests + capture trace during wmRelayout
Bug: 129389526
Change-Id: I352a3213f074377bd10721d16535c1e27fb2e746