Implement Unsubscribe in vhal proxy.

Implement the unsubscribe function in IVehicleHardware. This will
stop the server from generating property update events for the
specified [propId, areaId].

Test: atest GRPCVehicleHardwareUnitTest GRPCVehicleProxyServerUnitTest
Flag: EXEMPT hal change
Bug: 328316981
Merged-In: I35f4860eead0c8ec9b192657fe51cc0ff4319383
(cherry-picked from commit: cb00b1f816670c291044087db9f88cb76a2a9b3e)

Change-Id: I35f4860eead0c8ec9b192657fe51cc0ff4319383
diff --git a/automotive/vehicle/aidl/impl/proto/Android.bp b/automotive/vehicle/aidl/impl/proto/Android.bp
index c636bb9..b2edf75 100644
--- a/automotive/vehicle/aidl/impl/proto/Android.bp
+++ b/automotive/vehicle/aidl/impl/proto/Android.bp
@@ -52,6 +52,7 @@
         "android/hardware/automotive/vehicle/VehiclePropValueRequest.pb.h",
         "android/hardware/automotive/vehicle/SubscribeOptions.pb.h",
         "android/hardware/automotive/vehicle/SubscribeRequest.pb.h",
+        "android/hardware/automotive/vehicle/UnsubscribeRequest.pb.h",
     ],
 }
 
@@ -78,6 +79,7 @@
         "android/hardware/automotive/vehicle/VehiclePropValueRequest.pb.cc",
         "android/hardware/automotive/vehicle/SubscribeOptions.pb.cc",
         "android/hardware/automotive/vehicle/SubscribeRequest.pb.cc",
+        "android/hardware/automotive/vehicle/UnsubscribeRequest.pb.cc",
     ],
 }