[Backport 8.15] Add q parameter to Update By Query API (#2792) (#2795)

(cherry picked from commit afc1095)

Author: pquentin

output/openapi/elasticsearch-openapi.json

@@ -115,6 +115,10 @@ export interface Request extends RequestBase {
      * Random by default.
      */
     preference?: string
+    /**
+     * Query in the Lucene query string syntax.
+     */
+    q?: string
     /**
      * If `true`, Elasticsearch refreshes affected shards to make the operation visible to search.
      * @server_default false