[Flexiglass] Reset the tracked HUN row at the end of the touch

AmbientState was leaking the last mTrackedHeadsUpRow, because it was
never resetted. This CL resets it when HeadsUpTouchHelper receives an
ACTION_CANCEL up ACTION_UP event.

TouchHelpers were not receiving any more motion events after the user
has started an interaction with the shade (NSSL#isShadeBeingDragged()).
This CL keeps dispatching motion events to NSSL's TouchHelpers even
when we need to dispatch them to the scene framework.

Bug: 391204020
Test: check if AmbientState#mTrackedHeadsUpRow is resetted after swipes
      - receive a HUN
      - touch it (snooze, swipe down to open shade, any swipe)
      - finish the touch
      - dumpsysui AmbientState
Flag: com.android.systemui.scene_container
Change-Id: I6cdf739b9f8914f7fdfc9d3da65e5080036b06e7