Support forced display properties on secondary display

- Apply config_maxUiWidth to all displays.
- Forced size, density, scaling mode for non-default display are
  stored in DisplaySettings. The settings will apply when creating
  DisplayContent.
- Simplify WMS.displayReady because display policy would be updated
  via hierarchy of configuration container when config change happens
  from reconfigure.
- Remove WMS.displayReady(int) because the same things are done during
  initializing DisplayContent.
- Remove WMS.onDisplayAdded from Supervisor because during creating
  ActivityDisplay, DisplayWindowController, the DisplayContent will
  also be initialized. Without removing this, it may lost the settings
  that has been applied by configuring from the initial info again.
- Remove WMS.onDisplayRemoved from Supervisor because
  DisplayWindowController has handled it when removing container.

Bug: b/111362047
Test: atest DisplayContentTests
Test: atest DisplaySettingsTests
Test: atest ActivityManagerMultiDisplayTests

Change-Id: I5ae6f83db4c1264a32b7ce6a6951d3ba7e7fb662