Switch to GitHub based runners

[uncleDecart]

This is a temprorary measurement as we are investigating alternatives to BuildJet. Runners from BuildJet do not pick up our workflows and that affects us. We haven't received response in 2 weeks now, so I want to find an alternative. In the meantime, to stop the bleeding I want to switch to GitHub-based runners, they're slower, since they do not provide hardware virtualisation, so we expect workflow to run 1.5 hr instead of 45 minutes.