ci(docker): remove orphaned composite actions from legacy pipeline

combine-multi-arch-images, derive-image-names, and docker-build were
only ever used by the old docker-build-and-push* action family that
#7040 removed. With the bake-based pipeline in place the manifest
step is handled by docker-manifest.yaml, image names come from the
tags() function in docker-bake.hcl, and the per-group build is a
reusable workflow instead of a composite action.

Signed-off-by: Mete Fatih Cırıt <mfc@autoware.org>

Author: xmfcx