Refactor SiteSettingsLoader class

FYI progress on new loader that works more like standard Drupal rendering happening here https://www.drupal.org/project/site_settings/issues/3395787 ✨ Provide new site settings loader that uses manage display, etc rather than flattening Needs work

Does not stop refactoring this loader as long as output is maintained as is for this loader to avoid breaking all the existing sites that use this module.

Things have moved on significantly in the 2x branch and major refactor has occurred. Thanks all for the work on this!

Changed to fixed instead to recognise the contribution and give credit as this

Automatically closed - issue fixed for 2 weeks with no activity.