Identify + configure suitable container repository for non-public build images

[sxa]

Both Linux/s390x and the new Windows container support use images which we are currently only storing locally on the build hosts instead of in a container registry. This is far from ideal and leaves us with single points of failure.
We should identify a suitable container registry that we authenticate to and push to those during the image creation and pull from the build.
Options:

• Dockerhub private registry (Subject to any licensing restrictions on those repositories)
• Azure Container Registry (Potentially best suited for our Windows Azure hosts
• GitHub container registry (ghcr.io)
• quay.io
• Self-hosted?
• Something else?
  Noting that the OpenJ9 team use a private repository so that is known to work well.

[sxa]

Dup of #3217 which I couldn't find when I was creating this ...