[Flexiglass] Fixes down swipe destinations to match old impl.

When locked, regardless of how many fingers are used, when swiping down
from the top edge of the display, navigates to the quick settings scene,
if not in split shade mode (in which case it goes to the shade scene).

Test: updated unit tests
Test: manually verified by swiping down from the top-edge with one and
with two fingers, when locked and unlocked. Also verified that dragging
down with one finger, not from the top edge, when locked - still goes to
the shade when split shade and when single shade.
Fix: 328812365
Bug: 328473018
Flag: ACONFIG com.android.systemui.scene_container DEVELOPMENT

Change-Id: I5fd81f7aae3f6f15e97ebfdf2728e119544b9549