Improve generators code base

Current generators code base is quite messy, since it's both result of porting and raw implementation, that requires some cleanup.

Things to do:

• Move the templates/methods that are not really common for two generators to the one that they belong to.
• Add the caching mechanism for the evaluated values.
• Add per-artifact generator classes, but not mess the various generator functionality in a single place.
• Reevaluate the common utilities and look for a better-structured conditions(like checking what type we generate and decide if it should have cref or value setter)