Register Runners against V2 servers (#2505)

* Parse runners and send publicKey

* wip

* Fix conflicts

* Cleanup

* Cleanup

* fix test

* fix test

* Add trace for broker message listener

* Feedback

* refactor

* remove dead code

* Remove old comment

src/Runner.Listener/Runner.cs

@@ -343,6 +343,7 @@ namespace GitHub.Runner.Listener
         {
             if (settings.UseV2Flow)
             {
+                Trace.Info($"Using BrokerMessageListener");
                 var brokerListener = new BrokerMessageListener();
                 brokerListener.Initialize(HostContext);
                 return brokerListener;