Create publish-immutable-action workflow

[aeisenberg]

This PR creates a workflow that will publish an immutable action whenever a CodeQL Action release is created. We need to distinguish this from CodeQL Bundle releases to ensure that only the appropriate releases trigger the publishing process.

Merge / deployment checklist

• [x] Confirm this change is backwards compatible with existing workflows.
• [x] Confirm the readme has been updated if necessary.
• [x] Confirm the changelog has been updated if necessary.

[aeisenberg]

Don't merge yet. I want to make sure the release workflow is working properly first.

[aeisenberg]

@Jcambass, could you take a look to make sure this will be sufficient for immutable actions?

[aeisenberg]

Failures unrelated.