Redirect gcr.io to ghcr.io

[afrittoli]

We want to redirect gcr.io/tekton-releases/* to ghcr.io/tektoncd/*.
To do that, here are the planned steps:

• Move operator and results to ghcr.io, tracked in Reduce Cloud Storage / Container Registry Spending #2157
  Complete the migration to Artifact Registry (right now we have a canary redirect, so 5% of traffic is AR, 95% is container registry)
• Copy all images to ghcr.io, tracked in Copy all release images to gchr.io #2262
• Start the redirect
• Announce that all new Tekton releases are exclusively on ghcr.io and old releases are available on ghcr.io and downloading from gcr.io is deprecated.