Add ability to set Jira release from GH

[eriknelson]

I would like the ability to be able to set the Jira release, or fixVersion (the
jira field) from GH so that I can fully do my triage and alignment from GH.

We could use labels in a similar manner to the way that priority is used, ex:

release/v1.1.0
release v1.1.2

I would also want to be able to remove a release, which if priority is set
and triaged/accepted, would push the issue to the priority backlog (add the
label mtrho-priority-backlog).

If a GH issue gets a release, then the mtrho-priority-backlog label should
be cleared from the Jira.