Alerting: Support for imported Templates (#114196)

* refactor template service to contstruct notification template in one place, get provenance before creating and calculate resource version after.
* refactor get by UID and name

* introduce template kind in NotificationTemplate
* introduce includeImported flag and use in the k8s api
* support imported templates
* add kind to template uid
* tests for imported templates
* update API model
* set kind to default templates

pkg/tests/apis/openapi_snapshots/notifications.alerting.grafana.app-v0alpha1.json

@@ -3783,18 +3783,29 @@
         "type": "object",
         "required": [
           "title",
-          "content"
+          "content",
+          "kind"
         ],
         "properties": {
           "content": {
             "type": "string"
           },
+          "kind": {
+            "$ref": "#/components/schemas/com.github.grafana.grafana.apps.alerting.notifications.pkg.apis.alertingnotifications.v0alpha1.TemplateGroupTemplateKind"
+          },
           "title": {
             "type": "string"
           }
         },
         "additionalProperties": false
       },
+      "com.github.grafana.grafana.apps.alerting.notifications.pkg.apis.alertingnotifications.v0alpha1.TemplateGroupTemplateKind": {
+        "type": "string",
+        "enum": [
+          "grafana",
+          "mimir"
+        ]
+      },
       "com.github.grafana.grafana.apps.alerting.notifications.pkg.apis.alertingnotifications.v0alpha1.TimeInterval": {
         "type": "object",
         "required": [