CI: publish GitHub prerelease from master branch

## Problem

We have a prerelease pipeline that is always running. But the artifact is not published publically.

## Proposal

Always publish the artifact from the prerelease pipeline, with the GitHub `prerelease` flag.

Locate the prerelease pipeline configuration and inspect how artifacts from the master branch are currently built. Update the pipeline so every prerelease artifact is published publicly as a GitHub prerelease. Verify the workflow completes successfully and that the resulting GitHub release has the prerelease flag.

Written by the indexing model from the issue text.