Add Occluded Scene

Removes specific scene container logic that would simulate an
occluded state in flexi, and adds a dedicated scene with STL
animations. Provides compatibility with KTF by modifying the
existing animations.

Moves all logic to determine occluded state into
KeyguardOcclusionInteractor, and also ensures that the tests
are in the correct keyguard package.

Fixes: 436836037
Test: atest KeyguardOccludedInteractorTest SceneContainerStartableTest
Flag: com.android.systemui.scene_container
Change-Id: I32ff2f8683977cd08011417913a55134d358d71a