QuickSettings: visual updates.

- Update style for do not disturb subhead.
- Fix strict mode warning setting zen from volume panel.
- Longer delay in volume panel when expanded.
- Update zen icons.
- Update header peek height.
- Update detail pane back icon.

Bug:15186962
Change-Id: Icb8b95656f866bf9b0aa076d0b85c019a77e76c0
11 files changed