QS visual updates for P

- Black status bar area up top
- Gradient view behind QQS area
- Added stub view for system icon area
- Most things are parameterized for qs_header_system_icons_area_height,
so this can be moved and overlaid for devices with a notch

Test: visual
Bug: 70799006
Bug: 63772836
Change-Id: Iee3a975f50d572084de370d1b183a37f5e8e9e1a