Introduce NodeStatsLevel enum for nodes stats API

It supports 'node' instead of 'cluster' like Level, which is really
ClusterStatsLevel.

Author: pquentin

output/openapi/elasticsearch-openapi.json

@@ -245,7 +245,14 @@ export enum HttpMethod {
   HEAD
 }
 
+// This is the ClusterStatsLevel enum in Elasticsearch
 export enum Level {
+  cluster,
+  indices,
+  shards
+}
+
+export enum NodeStatsLevel {
   node,
   indices,
   shards

output/schema/schema.json

@@ -18,7 +18,7 @@
  */
 
 import { RequestBase } from '@_types/Base'
-import { Fields, Level, Metrics, NodeIds } from '@_types/common'
+import { Fields, Metrics, NodeIds, NodeStatsLevel } from '@_types/common'
 import { Duration } from '@_types/Time'
 
 /**
@@ -82,7 +82,7 @@ export interface Request extends RequestBase {
      */
     include_segment_file_sizes?: boolean
     /** Indicates whether statistics are aggregated at the cluster, index, or shard level. */
-    level?: Level
+    level?: NodeStatsLevel
     /**
      * Period to wait for a response. If no response is received before the timeout expires, the request fails and returns an error.
      * @server_default 30s