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/grpc/GRPCVehicleProxyServer.cpp b/automotive/vehicle/aidl/impl/grpc/GRPCVehicleProxyServer.cpp
index 558ab2f..a6abfa3 100644
--- a/automotive/vehicle/aidl/impl/grpc/GRPCVehicleProxyServer.cpp
+++ b/automotive/vehicle/aidl/impl/grpc/GRPCVehicleProxyServer.cpp
@@ -175,6 +175,16 @@
     return ::grpc::Status::OK;
 }
 
+::grpc::Status GrpcVehicleProxyServer::Unsubscribe(::grpc::ServerContext* context,
+                                                   const proto::UnsubscribeRequest* request,
+                                                   proto::VehicleHalCallStatus* status) {
+    int32_t propId = request->prop_id();
+    int32_t areaId = request->area_id();
+    const auto status_code = mHardware->unsubscribe(propId, areaId);
+    status->set_status_code(static_cast<proto::StatusCode>(status_code));
+    return ::grpc::Status::OK;
+}
+
 ::grpc::Status GrpcVehicleProxyServer::CheckHealth(::grpc::ServerContext* context,
                                                    const ::google::protobuf::Empty*,
                                                    proto::VehicleHalCallStatus* status) {