[Flexiglass] Replace NSSL.isInsideQsHeader with using the scrim bounds

The NSSL was using the QsHeader bounds to determine if a touch event can
be used for scrolling. NSSL shouldn't know about the QsHeader at all,
but receive bounds information about a scrollable region. This CL starts
to use the scrim bounds as that region.

Also fixes fixes the NSSLTest.transformEventForView helper function by
swapping the x y parameters.

Fixes: 312473478
Test: verify that we don't scroll nssl with events outside the scrim
Flag: com.android.systemui.scene_container
Change-Id: I5b3a45f384e959836d6f7b75bb947e3a851073a2