v3.3.1 cern rebase

This PR rebases our downstream changes on top of upstream v3.3.0. The only difference between v3.2.1-cern (actually 3.3.1) and v3.3.1 (upstream) now is that we're adding .gitlab-ci.yml used to push the chart to Harbor.

All previous changes regarding container image repo URLs (and other unrelated to Helm charts) have been reverted back to their original form -- exactly what upstream uses. Image mirror gitlab-registry.cern.ch/cloud/atomic-system-containers can be then set via the CERN Helm meta-chart.