Assign display groups to individual physical displays

- "displayGroup" attribute is added to display layout configuration.
- If displayGroup is null, the default display group is assigned to
  the display.
- The displays under the same displayGroup are assigned to the same
  display group.
- To not break backward compatibility, the default value of
  "displayGroup" is null.
- A power group corresponding to each display group is created when the
  boot phase is PHASE_SYSTEM_SERVICES_READY.

Bug: 254542024
Test: atest android.os.cts.PowerManagerTest PowerManagerServiceTest
      PowerManagerServiceMockingTest PowerManagerServicePermissionTest
      PowerManager_WakeLockTest PowerManager_ThermalTest
      android.os.PowerManagerTest WakeLockTest PowerGroupTest
      LogicalDisplayTest LogicalDisplayMapperTest
      DisplayManagerServiceTest LocalDisplayAdapterTest
      WakelockControllerTest DisplayPowerControllerTest
      DisplayPowerController2Test
Test: lunch gcar_md_emu_x86_64-userdebug && build && run emulator && adb
      shell dumpsys display && make sure each physical display has a
      different display group
Change-Id: Ieb42280f1a42e9d1353cb02ca3c1773fa1c50293