Add Open Social default permissions for site settings and menu link route

Problem/Motivation

- Add our own route subscriber to check the permissions.
- Make sure we assign those permissions to our default roles

Proposed resolution

   // Override the permission for the site settings route.
    // Which uses administer site configuration as permission, which
    // is used in too many places and we don't want to give that out.
    if ($route = $collection->get('system.site_information_settings')) {
      $route->setRequirements([
        '_permission' => 'administer social site configuration',
      ]);
    }

    // Override the permission for the menu link route.
    // Also see social_core_menu_link_content_access().
    if ($route = $collection->get('entity.menu.add_link_form')) {
      $route->setRequirements([
        '_permission' => 'administer social menu links',
      ]);
    }