Navigation: Use new page layout in Service accounts item page (#54200)

* use navId, pageNav and update alignments of service account page

* Fixing item header when feature is disabled

* Fix orgs item page

* Minor tweak to subtitle for service account item page

Co-authored-by: Torkel Ödegaard <torkel@grafana.com>

public/app/core/components/Page/Page.tsx

@@ -2,7 +2,7 @@
 import { css, cx } from '@emotion/css';
 import React from 'react';
 
-import { GrafanaTheme2, NavModel, NavModelItem } from '@grafana/data';
+import { GrafanaTheme2 } from '@grafana/data';
 import { config } from '@grafana/runtime';
 import { CustomScrollbar, useStyles2 } from '@grafana/ui';
 
@@ -32,7 +32,7 @@ export const OldPage: PageType = ({
 
   usePageTitle(navModel, pageNav);
 
-  const pageHeaderNav = getPageHeaderNav(navModel, pageNav);
+  const pageHeaderNav = pageNav ?? navModel?.main;
 
   return (
     <div className={cx(styles.wrapper, className)}>
@@ -59,14 +59,6 @@ export const OldPage: PageType = ({
   );
 };
 
-function getPageHeaderNav(navModel?: NavModel, pageNav?: NavModelItem): NavModelItem | undefined {
-  if (pageNav?.children && pageNav.children.length > 0) {
-    return pageNav;
-  }
-
-  return navModel?.main;
-}
-
 OldPage.Header = PageHeader;
 OldPage.Contents = PageContents;
 OldPage.OldNavOnly = OldNavOnly;