Moved NestedScrollConnection into SwipeToScene

This change allows us to consume all nested scroll gestures of the
scrollable elements in the scene without having to specify an additional
 modifier above the scrollable components.
The SceneTransitionLayout now has a default nested scroll behavior that
can be changed via the previous nestedScrollToScene() modifier.

Test: atest NestedScrollToSceneTest
Test: atest ElementTest (nestedScrollToScene is not mandatory anymore)
Test: Manually tested on Flexiglass
Bug: 336710600
Flag: com.android.systemui.scene_container
Change-Id: Icade65f33b84a9784aef599a62d0485dc65088db