Support device-specific DeviceStatePolicy

Adds support for providing a device-specific DeviceStatePolicy by
overriding the new config_deviceSpecificDeviceStatePolicy property.
Allowing OEM to implement DeviceStatePolicy that's not XML-based.

Test: atest DeviceStateManagerServiceTest
Test: atest DeviceStateProviderImplTest
Test: atest DeviceStateTest
Test: atest OverrideRequestControllerTest
Test: atest CtsDeviceStateManagerTestCases
Test: atest DeviceStatePolicyProviderTest
Bug: 205746479
Change-Id: I104b9c3bcd885727a1e0d0456b047eee27ed9c1b