gitlab-ci: Organize images using new REPO_SUFFIX templates feature

gitlab-ci: Organize images using new REPO_SUFFIX templates feature

Two benefits:

Most docker image related environment variables can now be defined in
the jobs where they're used instead of globally. The DEBIAN_TAG values
are propagated to other jobs via YAML anchors.

Images on https://gitlab.freedesktop.org/mesa/mesa/container_registry
are now organized in separate repositories with a suffix matching the
name of the job which makes sure the image is there.

Acked-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>