Update image references to use fully qualified names.

[hhiroshell]

Summary

This PR updates references to container images to use fully qualified image names for improving Podman (and more) compatibility, addressing #1218 .

Output

N/A

Documentation

• Should this change be documented?
  • [ ] Yes, see #___
  • [x] No

Since the pack's behavior will not change, there is nothing new to add to the documentation. On the other hand, it is desirable that image names already written in documents, such as sample commands and builder names, be specified with the full name. It will be addressed with https://github.com/buildpacks/docs/pull/702 .

Related

Resolves #1218