Allow override requests to outlive the requesting process.

This change introduces a flag, FLAG_CANCEL_STICKY_REQUESTS, on the
device states that are provided by the DeviceStateProvider. If the flag
is set on a device state it indicates that the device state should
cancel any outstanding sticky requests when entered. If at least one
device state is configured to be a terminal device state (has the flag
set) the service will be configured to allow sticky requests, otherwise
requests will continue to be cancelled when the requesting process dies.

Fixes: 192671286

Test: atest DeviceStateManagerServiceTest
Test: atest DeviceStateProviderImplTest
Test: atest DeviceStateTest
Test: atest OverrideRequestControllerTest
Change-Id: I7a6bdc9334342fa818920b56a4f0c22629bb101f