Add separate release workflow

[blink1073]

Summary of changes

Adds an extra discriminator for ${{ github.ref }} in the concurrency group.
This avoids a race condition in workflow runs which caused the release job to be canceled for either a tag or a commit with the same sha.

Part of #3093

Pull Request Checklist

• Changes have tests
• News fragment added in changelog.d/. N/A
  (See documentation for details)

[abravalheri]

Hi @blink1073 thank you very much for providing this PR!

I was trying to go through GitHub's docs trying to understand this config with release: types: [published].

Does this solve the problem with tests never running discussed in #3093 (comment)?

[blink1073]

The latest commit effectively restores the original behavior before concurrency limiting as much as possible. The only difference is that we don't run the unit tests explicitly before release.

[abravalheri]

I was not expecting how more annoying PyPy+Windows tests can be...
It is like they are just waiting to fail in different ways...

[blink1073]

Yeah, it is pain squared

[blink1073]

Okay, with the latest change I believe we have what we want. We avoid canceling subsequent pushes and pushes that are to different git references, refs/head/main vs refs/tags/foo.

[blink1073]

Closing in favor of #3116