[flexiglass] Crash when switching to incorrect shades

Reintroduces a protection that we used to have before ag/31525022 that
was based on crashing when switching to scenes or overlays that weren't
in the SceneContainerConfig. This time it's done in the validate
methods.

Flag: com.android.systemui.scene_container
Fix: 394632852
Test: unit tests added
Change-Id: I810abd687d2beb95bf5aae87a76d7db1fc765c93