add assignment resource id to the schema (#10309)

Author: eshaparmar

specification/guestconfiguration/resource-manager/Microsoft.GuestConfiguration/stable/2020-06-25/guestconfiguration.json

@@ -1250,6 +1250,11 @@
             "Pending"
           ]
         },
+        "resourceId": {
+          "type": "string",
+          "readOnly": true,
+          "description": "Name of the guest configuration assignment resource setting."
+        },
         "reasons": {
           "type": "array",
           "items": {