Dragging on launcher background on external display didn't do anything
because there was no StatusBarTouchController. Now by adding it to
SecondaryDragLayer, we can open the shade on external display via
launcher drag
Bug: 362719719
Bug: 416511740
Test: manual testing
Flag: EXEMPT refactor only
Change-Id: I1a587fe85bf2e7c6f212b3358646d5d282019eef