STL NestedScrollHandler uses the current Content

The scroll gesture is now being intercepted by SceneTransitionLayout if
the NestedScrollHandler finds that the current Content allows for it.

Test: atest DraggableHandlerTest
Bug: 377503459
Flag: com.android.systemui.scene_container
Change-Id: I2e97d365b23775a4ecad5d81327460299606488f
3 files changed