Admin pages now grant access if the user has access to any of the child pages

#296693: Restrict access to empty top level administration pages introduced a bug in the SystemAdminMenuBlockAccessCheck whereby if a user didn't have access to the first child of an admin block page, access was denied.

#3413508: Admin page access denied even when access is given to child items fixed this to grant access to these admin pages if the user has access to any of the children pages.

This applies to any admin page with the _access_admin_menu_block_page or _access_admin_overview_page requirements applied. These requirements are automatically added to any route using the Drupal\system\Controller\SystemController::systemAdminMenuBlockPage or Drupal\system\Controller\SystemController::overview callbacks.