Fix fullsceen task asumption

Activity Embedding CTS assumes task bounds always fill
the TDA. However, it isn't always if OEMs have it's customization.

This CL fix the assumption by using the task bounds in WMState.

It also remove the BoundsChange reated logic because we wait for bounds
change instead.

Bug: 292187837
Bug: 302112669
Bug: 302192873
Test: atest cts/tests/framework/base/windowmanager/jetpack/src/android/server/wm/jetpack/embedding
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:113db95b5f3de0804631929f8c0f6d1438ff8190)
Merged-In: If7e28ae5beb3a9fa5dce4ad613cd74479606e388
Change-Id: If7e28ae5beb3a9fa5dce4ad613cd74479606e388