Serialize "request_seq" as int in debug adapter

Previously we had been serializing "request_seq" as a string in our
reponses to VS Code's debug adapter client.  Very recently their code
changed such that our responses were no longer being handled correctly.
This is due to a change on their side which assumes that "request_seq"
will always be returned as an int.  This change corrects that in our debug
adapter message serialization.

Author: daviwil

src/PowerShellEditorServices.Protocol/MessageProtocol/Serializers/V8MessageSerializer.cs

@@ -34,8 +34,11 @@ public JObject SerializeMessage(Message message)
             }
             else if (message.MessageType == MessageType.Response)
             {
+                int messageId = 0;
+                int.TryParse(message.Id, out messageId);
+
                 messageObject.Add("type", JToken.FromObject("response"));
-                messageObject.Add("request_seq", JToken.FromObject(message.Id));
+                messageObject.Add("request_seq", JToken.FromObject(messageId));
                 messageObject.Add("command", message.Method);
 
                 if (message.Error != null)