Better release asset management

Current release assets directly link to artifact.

Meaning old release artifact are no longer accessible once a new version is released. Only the source code remain consistent with the version. We have two solutions here:

• remove the links to artifacts for older release.
• try a better management with version specific permalink as specified: https://docs.gitlab.com/ee/user/project/releases/#permanent-links-to-release-assets

I'd recommend the later as the former does not really make sense with the concept of releases. But it may require a bit of work and planning. It should be discussed/debated when we have the time, and IF necessary.