XWIKI-12772: Create extension points for the top menu and stop hardcoding its content.

* Fix tests.

xwiki-platform-core/xwiki-platform-test/xwiki-platform-test-ui/src/main/java/org/xwiki/test/ui/po/BasePage.java

@@ -149,8 +149,7 @@ public String getHTMLMetaDataValue(String metaName)
      */
     public boolean isAuthenticated()
     {
-        return getDriver().hasElementWithoutWaiting(
-                By.xpath("//div[@id='xwikimainmenu']//li[contains(@class, 'navbar-avatar')]//img"));
+        return getDriver().hasElementWithoutWaiting(By.id("tmUser"));
     }
 
     /**