Improve ContentScope.layoutState for Nested STLs

This CL makes the transition state utilities in ContentScope.layoutState
(isTransitioning(Between|FromOrTo)) consider ancestor states too, so
that it is easier for STL users to introduce nested STLs without having
to change the checks in existing scenes.

Bug: 438951613
Test: NestedSceneTransitionLayoutStateTest
Flag: com.android.systemui.scene_container
Change-Id: I31093c10858d8ea9e091949a0a5a3e6e6e0b2aa8