[flexiglass] Check if there are duplicate scenes with the same key.

At Module level when init-ing with the scenes, do a check to see if
there are any duplicate scenes with the same SceneKey since that is not
expected.

Bug: None
Test: Manually provide module with the same key, see crash
Flag: ACONFIG com.android.systemui.scene_container DEVELOPMENT
Change-Id: I3e555e2492b2328c66a221f68e07a9f6b52bd4e0