Re-adds flags for device state manager configuration

Re-adds the ability to process flags in the configuration
files for device state manager. This will allow the aosp
image to be compatible with previous vendor images.

Devices should still be updated to use the updated property
values for their device state configuration, but devices without
an updated vendor image would fail without this change.

Flag: android.hardware.devicestate.feature.flags.device_state_configuration_flag
Bug: 388366842
Test: DeviceStateProviderImplTest
Change-Id: Iafe2a76418173baaf116fdc0e47cc7726f77287f