message: core-app-api: bring back element discovery for AppManager
diff: @@ -222,7 +222,7 @@ export class AppManager implements BackstageApp {
  const { routing, featureFlags, routeBindings } = useMemo(() => {
  const result = traverseElementTree({
  root: children,
  - discoverers: [childDiscoverer],
  + discoverers: [childDiscoverer, routeElementDiscoverer],
  collectors: {
  routing: routingV2Collector,
  collectedPlugins: pluginCollector,
  