[CS] Make NPVC and QuickSettingsController singletons.

Most of this change is having ShadeController rely on the
ShadeViewController interface instead of on
NotificationPanelViewController directly, which required adding some
additional methods to ShadeViewController.

Bug: 277762009
Test: verified keyguard bottom area works with MIGRATE_INDICATION_AREA
flag off and on (verified indication text updates based on events,
updates based on font changes)
Test: verify shade works: displays notifs, notifs can be expanded,
notifs can be swiped away, shade reinflated on font change, etc.
Test: verify QS works: tiles display, tiles update based on taps, etc.

Test: atest CentralSurfacesImplTest ShadeControllerImplTest
NotificationPanelViewControllerTest

Change-Id: Ib2cb857374a094402898b5179ed9fb7b4e399035