STL may not consume gesture during overscroll

New Behavior: STL no longer consumes the drag gesture by default. When
we get an OverscrollSpec without transitions, it tells STL to stop
handling the gesture. This gives its ancestor nested scroll nodes a
chance to handle it.

Test: atest SwipeToSceneTest
Test: atest DraggableHandlerTest
Bug: 336710600
Flag: com.android.systemui.scene_container
Change-Id: Id565b9a8f1fe52793caa8ad07b6d74718dacb78c