Do release in two stages

[mx-psi]

To avoid having to re-tag and catch issues earlier, we can have a two stage approach to the release: we first create the artifacts and have them in some sort of 'staging' state, and the actual release step consists in moving said artifacts to the places where users expect them. We could do this with two sets of tags or with a workflow for staging + a tag for the actual release.

One very small step in that direction is #772