Alerting: Get grafana-managed alert rule by UID (#86845)

* Add auth checks and test

* Check user is authorized to view rule and add tests

* Change naming

* Update Swagger params

* Update auth test and swagger gen

* Update swagger gen

* Change response to GettableExtendedRuleNode

* openapi3-gen

* Update tests with refactors models pkg

pkg/services/ngalert/api/tooling/api.json

@@ -4546,7 +4546,6 @@
    "type": "object"
   },
   "gettableAlert": {
-   "description": "GettableAlert gettable alert",
    "properties": {
     "annotations": {
      "$ref": "#/definitions/labelSet"
@@ -4608,6 +4607,7 @@
    "type": "array"
   },
   "gettableSilence": {
+   "description": "GettableSilence gettable silence",
    "properties": {
     "comment": {
      "description": "comment",
@@ -4807,7 +4807,6 @@
    "type": "array"
   },
   "postableSilence": {
-   "description": "PostableSilence postable silence",
    "properties": {
     "comment": {
      "description": "comment",