[flexiglass] Adds TransitionKey support.

In order to support the new TransitionKey API in SceneTransitionLayout
(STL), we integrate the SceneDataSource from the previous CL.

The CL also adds instant- and faster-shade collapse transitions.

Bug: 323173116
Test: unit tests updated
Test: manual verification on phone of the following scenes: lockscreen
-> bouncer -> shade -> quick settings (unlock) -> gone -> shade > quick
settings
Flag: ACONFIG com.android.systemui.scene_container DEVELOPMENT

Change-Id: I30ea3d7c2ace8bad9ad2999bdbde16e71337bca2