Move handleCompleteDeferredRemoval to animator thread

The method may remove window hierarchy element in random
timing (usually depends on animation). If the caller
indirectly calls to performSurfacePlacement inside a loop
that also removes element, the loop may encounter index
out of bound exception. It is hard for the caller to aware
how to iterate window containers safely.

Because performSurfacePlacement always calls WindowAnimator
scheduleAnimationLocked, the movement of invocation should
not miss the original cases for deferred removal.

It also reduces unnecessary invocations up to 50% because
animator won't execute multiple times if it is scheduled,
while performSurfacePlacement calls each time. And the
partial cost may be moved out from binder thread.

Bug: 173270358
Test: CtsWindowManagerDeviceTestCases
Change-Id: If9a45403e7bbedb2073f8e6f6e90934af0c4c29e