Add Agent Job and Job Step request handlers (#635)

* Stage changes

* Fix update job request handler

* WIP

* Additional agent handler updates

* Setup agent job step create test

* Fix Step update handler

src/Microsoft.SqlTools.ServiceLayer/Agent/Contracts/AgentJobStepInfo.cs

@@ -13,6 +13,8 @@ namespace Microsoft.SqlTools.ServiceLayer.Agent.Contracts
     {
         public string JobId { get; set; }
 
+        public string JobName { get; set; }
+
         public string Script { get; set; }
 
         public string ScriptName { get; set; }