Remove _entity from site settings entity type IDs

Thanks for starting on this!

I think the bigger challenge here is the update hook to use entity update manager to copy existing site settings entities and type entities to the new entities. Tests from gitlab pipelines needs looking at as well.

Thanks!

Probably this is just going to be too much effort to actually make it happen. Going to leave it parked. Annoyingly I created this module back in 2016 when A) Drupal 8 was new and B) I did not really know what I was doing. This may just remain a hangover of that unfortunately.