Add Katello as owners of Katello packages

[ekohl]

This is a draft because it warrants some discussion. The goal is to implement https://community.theforeman.org/t/per-package-merge-permissions-in-foreman-packaging-for-plugin-maintainers/39372 for Katello.

First of all, the katello group currently doesn't exist because we can't refer to groups from other organizations.

Then we should also consider the implications.

• Do we want all Katello devs to be able to merge this, or limit it?
• https://github.com/theforeman/theforeman-rel-eng/blob/master/procedures/katello/release.md.erb has steps that the release engineer bumps the packages & merge it. Should we move that to the @theforeman/katello-release-owners group as well so it can move along faster? We already allow other plugin owners to merge their own updates via code owners.