Fixes #37859 - Re-drop evr extension in katello

[sjha4]

What are the changes introduced in this pull request?

This brings back the changes from #11087 which were reverted as part of #11103 to stop blocking 4.14.

Considerations taken when implementing this change?

Also pulled in some updates from #11098 which came out of additional reviews on the first katello PR.

What are the testing steps for this pull request?

Same as testing steps for #11087
Check sudo rpm -qa evr
Remove the rpm: sudo rpm -e evr_package_from_above
Run bundle exec rails katello:reset to mimic fresh installs
Test the usual flows with applicability
To test existing systems just delete the evr package and make sure everything continues to work as normal.

[ianballou]

This is working fine still! I think it's safe to merge even now, yeah? We could also wait until we learn more about how remote databases will deal with the changes, up to you. Worst case we have another revert (but I really hope not!)

[ianballou]

What do you think about adding an error if the permissions aren't sufficient?

[ianballou]

Since I don't think my previous comment is important anymore, ACK