Window Manager Flag Migration (10/n)

Refine the APIs of system bar appearance/behavior:
- Add getters
- Let the caller can only change certain appearance flags with out
  touching others
- Adjust appearance/behavior for the legacy apps if they don't uses the
  new APIs

Bug: 118118435
Test: atest InsetsSourceProviderTest InsetsStateControllerTest
            InsetsPolicyTest WindowStateTests CommandQueueTest
            RegisterStatusBarResultTest InsetsFlagsTest
            LightBarControllerTest RegisterStatusBarResultTest
            ViewRootImplTest DisplayPolicyLayoutTests
            DisplayPolicyInsetsTests DisplayPolicyTests
            TaskSnapshotSurfaceTest

Change-Id: I388decc9dc9b617348a6352b81fe77a19f27a0d7