Add missing config hinting

It's not well documented in Drupal (it took me a while to find anything about this) and I saw that `#config` was changed to `#config_data_store` in the newer Drupal versions.

In this issue of Drupal core they are talking about the fact that Drupal should indicate if a config value was overridden. So, for newer Drupal in the future, it would be recommended to add `#config_data_store`. Please see https://www.drupal.org/project/drupal/issues/2408549 🐛 There is no indication on configuration forms if there are overridden values Needs work

Seems like it will be postponed on 🐛 There is no indication on configuration forms if there are overridden values Needs work