NetworkObserver codebase makes it hard to only trigger Override and LocalMode hooks for DevTools requests. So start observing DevTools requests in light of upcoming bug 2038986 and ignore them in the frontend until we have proper frontend implementation. Went for this intermediate simpler approach in order to try to uplift this patch for make the style editor work when using local mode. Differential Revision: https://phabricator.services.mozilla.com/D310056