Deprecate gcr.io/k8s-skaffold/pack usage to official CNB image at docker.io/buildpacksio/pack

Skaffold hosts a container image for running the Cloud Native Buildpack (CNB) project's pack command at gcr.io/k8s-skaffold/pack. We have tagged images for each version of pack that we have packaged in this way.
Our pack image was created to enable building with Buildpacks on Google Cloud Build. The source is found at: https://github.com/GoogleContainerTools/skaffold/tree/main/deploy/buildpacks

As the CNB project now maintains and distributes [their own image](https://hub.docker.com/r/buildpacksio/pack) (docker.io/buildpacksio/pack), we should deprecate Skaffold's pack image and move our users to the CNB-maintained image.

Related - [go/deprecate-skaffold-pack-image](https://goto.google.com/deprecate-skaffold-pack-image)