add alert rule template version to stable version of the API (Azure#18658)

Author: Amitbergman

specification/securityinsights/resource-manager/Microsoft.SecurityInsights/stable/2021-10-01/AlertRules.json

@@ -1418,6 +1418,10 @@
           "description": "The Name of the alert rule template used to create this rule.",
           "type": "string"
         },
+        "templateVersion": {
+          "description": "The version of the alert rule template used to create this rule - in format <a.b.c>, where all are numbers, for example 0 <1.0.2>",
+          "type": "string"
+        },
         "description": {
           "description": "The description of the alert rule.",
           "type": "string"