Update Spack version and build image/scripts
- Spack version updated to
v0.18.1
. - Build image base updated to
ubuntu:20.04
. - Fixes for pynn-brainscales, hxtorch packages for new version of Spack
- Update of CI pipelines for deployment to the Lab (installation script moved from inside the image to this repo, file transfer to the OKD job happens with git clone instead of rsync, one image used for building in all 3 OKD projects, general restructuring, minor changes here and there)