Migrate CI from GitLab to GitHub

[al3xa23]

This PR aims to change our .gitlab ci to GitHub Actions. Some things are not working yet like nix, but most of the containers for the distirbutions are build.
@leonardocarreras, feel free to have a look :)

[leonardocarreras]

Hi @al3xa23 thanks for merging the suggestions... Just a small summary of the stuff done:

• Turned on the nix build and packaging jobs
• Image names now come from the repo owner, so forks push to their own space
• Skip duplicate PR runs and cancel old ones
• Fixed image tags so odd PR names don't break them
• Faster builds with caching and reused steps
• Auto-cleanup of old images
• Updated the actions and turned on the pre-commit checks