Add Hard Drive metrics to vitals_extra

See merge request https://git.drupalcode.org/project/vitals_extra/-/merge_requests/4 for testing, or apply the patch https://git.drupalcode.org/project/vitals_extra/-/merge_requests/4.patch

MR 4 has been updated to be compatible with Drupal 11 because format_size() function is now remplaced by ByteSizeMarkup class.
See https://www.drupal.org/node/2999981 → change record for more information.