SystemUI: Follow light/dark theme in quick settings

Android 12's dual-tone style where the quick settings panel is always
dark makes the light theme look like a second-class citizen. Pure black
also looks out-of-place next to QS tiles and the notification panel
because dynamic themes don't affect it at all.

Revert to the ~Beta 1 style where quick settings used the same theme as
the notification shade.

- colorAccentPrimary has been replaced with colorAccent for contrast in
  light mode, because colorAccentPrimary is system_accent1_100 (dark
  accent color)
- Footer chips have been converted to surfaces (similar to QS tiles and
  notifications), which makes more sense with the new style
- The QS background is now the same as the notification shade background
  in both light and dark modes

Demo screenshots (with dual-tone commit):
https://twitter.com/kdrag0n/status/1445922541218922496

[kdrag0n: ported to 12L]

Change-Id: I3d45b72f0f119e100505409d178ab8f698993881