ghcr.io doesn't have retention policy settings

[iaingalloway]

Need to set one up with an action: https://github.com/marketplace/actions/container-retention-policy

Existing actions don't seem to support the functionality I want:

• https://github.com/snok/container-retention-policy needs a PAT
  • https://github.com/orgs/community/discussions/50123
  • Do you really need a personal access token? snok/container-retention-policy#27
  • Looks like it uses the user/org APIs to retrieve the packages (which will certainly need a PAT rather than GITHUB_TOKEN)
• https://github.com/marketplace/actions/ghcr-pruning needs a PAT
• https://github.com/bots-house/ghcr-delete-image-action needs a PAT
• https://github.com/actions/delete-package-versions doesn't support a very wide variety of policies
• None of them seem to support multi-arch images (they delete untagged images that are referenced from the multi-arch manifest)
  • Removing untagged images can damage tagged images snok/container-retention-policy#63
• https://github.com/DoodleScheduling/gh-package-retention supports multi-arch images and doesn't appear to need a PAT, but doesn't support a very wide variety of policies