Refs #7423: Convert to using Bastion core to provide the Katello UI.

This commit removes the components that have been transitioned to Bastion
core and changes the engine to bastion_katello. Further, dependencies
in both the re-named engine and Katello are removed that no longer apply.
Merge pull request #4754 from ehelms/refs-7423

Refs #7423: Convert to using Bastion core to provide the Katello UI.