Clean up system ui state flags

- Move setting of the flags to the responsible components, updating them
  directly instead of duplicating the logic in OverviewProxyService
- Add flags for tracking keyguard state, overview disabled state, and
  screen pinning state
- Ensure the notification expanded state excludes quicksettings
- Add logging for states and both back/assistant disabled states

Bug: 132107485
Bug: 131698989
Test: Immersive mode - ensure you can't swipe back, ensure you can't swipe
                       up or open the assistant
Test: Expanded notification - ensure back doesn't work when locked/unlocked
Test: Expanded QS - ensure back works when locked/unlocked
Test: A11Y - ensure that 2 finger swipe up shows accessibility menu
Test: A11Y - ensure that 2 finger swipe up & hold works
Test: Bouncer - launch notification over launcher, ensure back works,
 	        ensure assistant doesn't work
Test: Screen pinning - ensure back/assistant doesn't work

Change-Id: Ife37bf40602b997e6c2b534d9fa274ce07c53b07
Signed-off-by: Winson Chung <winsonc@google.com>