[Katello] Removing Old Auth System

Howdy,

Today a commit is going in to master that effectively removes the entirety
of the old Katello authorization system. This commit may requires
developers to do a full reset rake katello:reset (and in some instances,
if you notice a failing migration, running it a second time) if witnessing
strange behaviors. Similar to other changes we've made on our way to 2.0,
this effectively removes the old auth system as if it never existed
post-enginification.

Relevant PR - https://github.com/Katello/katello/pull/4329

Eric