AppPlugin: give full control to page layout when navigation is missing (#26247)

(cherry picked from commit 5f8eb93db1)

packages/grafana-data/src/types/app.ts

@@ -42,6 +42,10 @@ export class AppPlugin<T = KeyValue> extends GrafanaPlugin<AppPluginMeta<T>> {
   /**
    * Set the component displayed under:
    *   /a/${plugin-id}/*
+   *
+   * If the NavModel is configured, the page will have a managed frame, otheriwse it has full control.
+   *
+   * NOTE: this structure will change in 7.2+ so that it is managed with a normal react router
    */
   setRootPage(root: ComponentClass<AppRootProps<T>>, rootNav?: NavModel) {
     this.root = root;