Add orphaned LMS entity cleanup Drush command

Problem/Motivation

Sometimes it may happen that orphaned entities remain in the database somehow. It shouldn't ever be the case as we have cleanup logic implemented in entity delete hooks but.. past experience showed that such orphaned entities sometimes remain and may lead to unexpected errors like 🐛 Orphaned course status causes an exception Active or worst case just litter the database.

Proposed resolution

Create a cleanup Drush command.