Use Library for GitHub Actions Functionality and Allow Manual lineage_scan Runs

[mcdonnnj]

🗣 Description

This PR makes two changes:

• Adds the yanglbme/actions-toolkit library to provide an interface for GitHub Actions functionality.
• Adds workflow_dispatch functionality to the lineage_scan workflow so it can be manually triggered.

💭 Motivation and context

The yanglbme/actions-toolkit library provides a Python implementation of the GitHub maintained actions/toolkit JavaScript project. Currently it only has the actions.core package implemented, but this is also the functionality we are most interested in using. While we are only using the functionality to get Action inputs right now, I have plans to leverage more of the GitHub Actions functionality available and this library will provide a clean means to do so.

Adding a workflow_dispatch trigger to the lineage_scan workflow allows us to manually trigger a run either in the GitHub web UI or by using the GitHub CLI. This will provide some flexibility when a skeleton has a number of PRs to merge and tests take a notable amount of time to manually trigger the workflow if a scheduled run has processed mid-merges.

🧪 Testing

Automated tests pass. A manually triggered lineage_scan run was successful.

✅ 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]

Nice improvement - the future is bright! 😎