Generate Docker package url programmatically, without need of artifacts

Because of https://gitlab.com/gitlab-org/gitlab-ce/issues/33524 , our Docker builds are now broken. We can get rid of the necessity of artifact dependency by generating the URL ourselves. Right now we are downloading artifacts from dependent stage ONLY TO figure out the download URL (and we download it from that URL during docker build). So in effect, we are downloading the package twice.

This MR generates the download url progammatically.

Build - https://dev.gitlab.org/gitlab/omnibus-gitlab/-/jobs/1172164

Also closes: #2465 (closed)