Introduce WebSocket-based RPC v2 (#239)

* Introduce WebSocket-based RPC v2

* go test: add -ldflags="-B gobuildid"

* No need to change the "controller.workerNotifier.Notify()" error message

* No need to modify Protocol Buffers/gRPC generated code

* rpcWatch(): explain that connection shouldn't be normally be closed

* Avoid "port forwarding failed: " repetition in error messages

* Improve comments and avoid repetition in IP resolution errors

internal/tests/devcontroller/devcontroller.go

@@ -29,6 +29,9 @@ func StartIntegrationTestEnvironmentWithAdditionalOpts(
 ) (*client.Client, *controller.Controller, *worker.Worker) {
 	t.Setenv("ORCHARD_HOME", t.TempDir())
 
+	// Enable experimental RPC v2 by default in tests
+	additionalControllerOpts = append(additionalControllerOpts, controller.WithExperimentalRPCV2())
+
 	devController, devWorker, err := dev.CreateDevControllerAndWorker(t.TempDir(),
 		":0", nil, additionalControllerOpts, additionalWorkerOpts)
 	require.NoError(t, err)