Track the Python and Go versions we use for general GitHub Actions jobs

[mcdonnnj]

🗣 Description

This adds appropriate outputs to track the versions of Python and Go that should serve as "defaults" for use in our GitHub Actions workflows.

💭 Motivation and context

It's somewhat cumbersome to keep updating all the different versions hard-coded in workflows. It would make sense to reference the outputs of this Action unless specifically undesired.

🧪 Testing

Automated tests pass. This change is used in cisagov/skeleton-generic#157 to switch over to this change for our skeleton projects.

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• All new and existing tests pass.

[dav3r]

Good thinking 👍