MDL-45242 Lib: Replace calls to deprecated functions

In all cases changes have been kept to a minimum while not making
the code completely horrible. For example, there are many instances
where it would probably be better to rewrite a query entirely, but
I have not done that (in order to reduce the risk of changes).

lib/adminlib.php

@@ -4311,7 +4311,8 @@ class admin_setting_users_with_capability extends admin_setting_configmultiselec
                     'This is unexpected, and a problem because there is no way to pass these ' .
                     'parameters to get_users_by_capability. See MDL-34657.');
         }
-        $userfields = 'u.id, u.username, ' . get_all_user_name_fields(true, 'u');
+        $userfieldsapi = \core\user_fields::for_name();
+        $userfields = 'u.id, u.username, ' . $userfieldsapi->get_sql('u', false, '', '', false)->selects;
         $users = get_users_by_capability(context_system::instance(), $this->capability, $userfields, $sort);
         $this->choices = array(
             '$@NONE@$' => get_string('nobody'),