Update stable branch workflows

Notes about Katello:

We have a weekly triage meeting where we set the target version for every issue in a release.

We don’t pay much attention to the “Fixed In Version” value. In the past we had a TODO column like Foreman, but none of us Katello devs use it so it was neglected. We rely on tool_belt to tell us what needs cherry-picking (and for changelog creation+amendment too).

For cherry-picking, we cherry-pick at release time only. When it comes time to cherry pick, we use tool_belt. Assuming that the Katello version configuration has the proper “prior releases”, cherry-picks for a version or any older version that are in the prior releases list should show up with the ./tools.rb cherry-picks configs/katello/x.y.yaml command.

If the cherry-picks are clean, as in no conflicts, then the command output from tool_belt can be copy and pasted to perform all the necessary cherry-picks at once.