Change to pass Schema compare Operation id from ADS (#828)

* Changing that SC Operation id be passed from ADS and some test addition

* Fixing typos

src/Microsoft.SqlTools.ServiceLayer/SchemaCompare/Contracts/SchemaCompareRequest.cs

@@ -50,6 +50,11 @@ namespace Microsoft.SqlTools.ServiceLayer.SchemaCompare.Contracts
     /// </summary>
     public class SchemaCompareParams
     {
+        /// <summary>
+        /// Operation id of the schema compare operation
+        /// </summary>
+        public string OperationId { get; set; }
+
         /// <summary>
         /// Gets or sets the source endpoint info
         /// </summary>