[hook] use `serializer.doc_type` if exists (closes #17069804)

let serializer decide if cw_etype and doc_type is different

hooks.py

@@ -98,7 +98,7 @@
             # IFullTextIndex serializer, therefore the "id" and "doc_type" in
             # kwargs below must be container data.
             kwargs['id'] = json['eid']
-            kwargs['doc_type'] = json['cw_etype']
+            kwargs['doc_type'] = getattr(serializer, 'doc_type', json['cw_etype'])
             if json.get('parent'):
                 kwargs['parent'] = json.pop('parent')
             else:  # TODO only for types that have parents