NestedScrollToScene communicate desired behavior while scrolling

This CL introduces a new node but no new behavior.
The NestedScrollConnection will be moved to SwipeToScene, in a following
CL.

Test: Just a refactor
Bug: 336710600
Flag: com.android.systemui.scene_container
Change-Id: Ib3485505bb639d9bc84d52f0796ee65253624aba