Use AAOS side timestamp for VehiclePropValue.

Update the timestamp set by the host-side VHAL proxy server with
the Android-side timestamp at AAOS VHAL side. This makes sure that
we always expose VehiclePropValue that is perfectly synced with
Android elapsedRealtimeNano. This CL also adds logic to deal with
cases when a property update event or a get value result is outdated.

This CL updates the unit test to cover more cases and remove the flaky
test case that requires starting a local GRPC server.

Flag: EXEMPT HAL change
Test: atest GRPCVehicleHardwareUnitTest
Bug: 349678711
Change-Id: I5e2c07e77869f7286a438cb2a04d1b6c130c3c36