CI: Publish/release steps should be idempotent

[tjtelan]

The publish and release steps shouldn't fail if the steps are re-run. If a package+version is found to already exist, we should display a message saying so. But in CI, the "already exists" condition should not cause failure of the step.

This was found during some troubleshooting of our soon-to-be-deprecated packaging process. At one point, this was the case and it made running release less stressful.