Integrate GitHub actions debug mode detection

[webknjaz]

This should be possible by inspecting the following environment variables:

• RUNNER_DEBUG: https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/store-information-in-variables#default-environment-variables
• ACTIONS_RUNNER_DEBUG: https://docs.github.com/en/actions/monitoring-and-troubleshooting-workflows/troubleshooting-workflows/enabling-debug-logging#enabling-runner-diagnostic-logging
• ACTIONS_STEP_DEBUG: https://docs.github.com/en/actions/monitoring-and-troubleshooting-workflows/troubleshooting-workflows/enabling-debug-logging#enabling-step-debug-logging

There's additionally ${{ runner.debug }} to look at: https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/accessing-contextual-information-about-workflow-runs#runner-context.

Ref: https://docs.github.com/en/actions/managing-workflow-runs-and-deployments/managing-workflow-runs/re-running-workflows-and-jobs#about-re-running-workflows-and-jobs

We may also want to take the rerun attempt into account.

Could provide a skip-existing-on: rerun | debug | second/third-attempt or something.