Migrate release pipeline from Jenkins to Github Actions

[fbricon]

Red Hat's internal Jenkins pipeline is pretty annoying, tests are slow AF, timing out, it's inconvenient to use.

The only reason to use it is so a release can:

• deploy artifacts to JBoss Nexus
• rsync p2 repos to jboss.org

We could still perform Nexus deployment from Github actions, by configuring the credentials as github secrets. And instead of hosting the p2 repo to jboss.org, we could use Github releases instead, thanks to some JBang magic.