Migrate to Github Actions

[thomasferrandiz]

Issue: rancher/ecm-distro-tools#383

[github-advanced-security]

This pull request sets up GitHub code scanning for this repository. Once the scans have completed and the checks have passed, the analysis results for this pull request branch will appear on this overview. Once you merge this pull request, the 'Security' tab will show more code scanning analysis results (for example, for the default branch). Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results. For more information about GitHub code scanning, check out the documentation.

[pjbgf]

For reference, we did something similar in other repos, where you can still benefit from cross-arch cache while still being able to have arch-specific tags:
https://github.com/rancher/cis-operator/blob/master/.github/workflows/release.yml#L42-L44

May not be as relevant as we centralised the logic on the Makefile instead of leaning on GH actions.

[macedogm]

The main recommendation is to follow the least privilege when generating the token, as Paulo suggested.