This commit is multi-fold and impacts several areas:
- Don't re-generate final artifact locally if already present while
building with `requires_final_images`.
- Expose to CLI a way to build final images without pushing them.
- The packages listed with `requires_final_images` now are evaluated by
the solver so the full deptree is took into account
Fixes: https://github.com/mudler/luet/issues/294