Simplify step image promote inputs

Changes

This merge request simplifies how users specify where to publish container images in the promote step. Instead of requiring separate to_registry and to_repository parameters, users now provide a single to_image parameter that contains the complete destination image path.

- name: promote_image
  step: dist://step/oci/promote
  inputs:
    from_image: ${{ steps.build_image.outputs.image }}
    to_image: ${{ job.CI_REGISTRY_IMAGE }}

Subsequent changes also clean up dependencies on the promote step and optimize make targets to reduce calls to fetch dependencies.

Reference

• QOL improvements to step OCI image process (#255 - closed)