Simplify PriorityNestedScrollConnection

To simplify using PriorityNestedScrollConnection, we've reduced the
number of properties.
To stop scrolling, simply don't consume (return 0) the value received
during onScroll.

Test: atest PriorityNestedScrollConnectionTest
Bug: 370949877
Flag: com.android.systemui.scene_container
Change-Id: I03f4344299093ba3ebcba96cbe50ae6527fdff21