Add Grafana embed integration feature flag

lib/gitlab/gon_helper.rb

@@ -42,6 +42,9 @@ module Gitlab
       # Initialize gon.features with any flags that should be
       # made globally available to the frontend
       push_frontend_feature_flag(:suppress_ajax_navigation_errors, default_enabled: true)
+
+      # Flag controls a GFM feature used across many routes.
+      push_frontend_feature_flag(:gfm_grafana_integration)
     end
 
     # Exposes the state of a feature flag to the frontend code.