Correct swagger annotations for enums, status codes, and notification state (#37030)

## ⚠️ BREAKING ⚠️

- delete reaction endpoints is changed to return 204 No Content rather
than 200 with no content.

## Summary

Add swagger:enum annotations and migrate all enum comments from the
deprecated comma-separated format to JSON arrays. Introduce
NotifySubjectStateType with open/closed/merged values. Fix delete
reaction endpoints to return 204 instead of 200.

routers/api/v1/user/runners.go

@@ -40,7 +40,7 @@ func ListRunners(ctx *context.APIContext) {
 	//   required: false
 	// responses:
 	//   "200":
-	//     "$ref": "#/definitions/ActionRunnersResponse"
+	//     "$ref": "#/responses/RunnerList"
 	//   "400":
 	//     "$ref": "#/responses/error"
 	//   "404":
@@ -63,7 +63,7 @@ func GetRunner(ctx *context.APIContext) {
 	//   required: true
 	// responses:
 	//   "200":
-	//     "$ref": "#/definitions/ActionRunner"
+	//     "$ref": "#/responses/Runner"
 	//   "400":
 	//     "$ref": "#/responses/error"
 	//   "404":
@@ -115,7 +115,7 @@ func UpdateRunner(ctx *context.APIContext) {
 	//     "$ref": "#/definitions/EditActionRunnerOption"
 	// responses:
 	//   "200":
-	//     "$ref": "#/definitions/ActionRunner"
+	//     "$ref": "#/responses/Runner"
 	//   "400":
 	//     "$ref": "#/responses/error"
 	//   "404":