New unified werf cleanup procedure

[distorhead]

Implement new unified cleanup algorithm for all tagging strategies.

• Keep no more than N images related with N last commits for all git heads.
• Keep no more than N stages related with N last commits for all git heads.
• Keep all images that are being used in the Kubernetes.
• Keep all images that are recorded in the Helm release manifests.
• Stage can be cleared if it is not related with no HEAD and it is not used in Kubernetes and Helm.

[dmgtn]

Crazy drawings in Russian ))). As the author of them, I apologize. We are doing our best to make the design and decision making process public, but as we are a small team it sometimes seems easier to implement and than to document it, rather than going the right way. Sorry about that.