Fix ShadeTouchHandler over the lock screen

Shade expansion while on the lock screen is handled by the
NotificationShadeWindowViewController's DragDownHelper. In order for
the ShadeTouchHandler to work when opening the shade from the hub over
the lock screen, we need to simulate the full sequence of events for a
touch, since NSWVC has logic in both the dispatch and intercept phases.

This change also limits the ShadeTouchHandler to only accept downward
swipes. Upward swipes were not an issue over the dream, but it causes
some visual issues over the lock screen.

Fixed: 328838259
Bug: 335505186
Test: atest ShadeTouchHandlerTest CommunalTouchHandlerTest NotificationShadeWindowViewControllerTest
      also verified manually, see bug for video
Flag: ACONFIG com.android.systemui.communal_hub TEAMFOOD
Change-Id: I92b9c220b52b0c0677712fcda6ace27dff143ffa