enforce retention policy on staging registries

[BenTheElder]

@upodroid mentioned he'd already announced that staging registries would have a 90d retention policy, some of them accumulated a LOT of content, and secondarily we're also seeing them used sometimes like "production" with end users being directed to (or choosing on their own) to pull directly from gcr.io/k8s-staging-foo even though these are meant to be project internal and do not give us flexibility to reroute load / costs unlike registry.k8s.io

This issue tracks rollout to any remaining projects, AIUI the projects with the most data had a policy enabled but not all of them yet.

/sig k8s-infra
/priority important-soon
/assign @upodroid