Integrate generate script with task service (#426)

* Support generate script for backup

* change

* update task service data contract for Generate Script

* more changes

* update test

* add comments

* Add missing files

* update stub backup operation for testing

* pr comments

* remove empty space

* Fix tests

* Add unit/integration tests and isCancelable to TaskInfo

* address pr comments

* pr comments - fix tests

* fix minor issue

* fix minor issues

* remove unused variable

src/Microsoft.SqlTools.ServiceLayer/Localization/sr.resx

@@ -1811,15 +1811,15 @@
     <value>No Applicable Filegroup</value>
     <comment></comment>
   </data>
-  <data name="Backup_TaskName" xml:space="preserve">
+  <data name="BackupTaskName" xml:space="preserve">
     <value>Backup Database</value>
     <comment></comment>
   </data>
-  <data name="Task_InProgress" xml:space="preserve">
+  <data name="TaskInProgress" xml:space="preserve">
     <value>In progress</value>
     <comment></comment>
   </data>
-  <data name="Task_Completed" xml:space="preserve">
+  <data name="TaskCompleted" xml:space="preserve">
     <value>Completed</value>
     <comment></comment>
   </data>
@@ -1915,4 +1915,8 @@
     <value>The last backup taken ({0})</value>
     <comment></comment>
   </data>
+  <data name="ScriptTaskName" xml:space="preserve">
+    <value>scripting</value>
+    <comment></comment>
+  </data>
 </root>