Update tooling and automations

[kasparsd]

trafficstars

• Deprecate Vagrant and use only Docker.
• Replace Travis CI with GitHub Actions.
• Replace Docker Hub with GitHub Packages for custom Docker image hosting.

Checklist

• [ ] Project documentation has been updated to reflect the changes in this pull request, if applicable.
• [ ] I have tested the changes in the local development environment (see contributing.md).
• [x] I have added phpunit tests.

Release Changelog

• Tooling: Move from Travis CI to GitHub Actions for automations and Docker image hosting.