Identify suitable off-machine location for storing private build container images

[sxa]

Due to licensing issues we cannot ship the RHEL/s390x build image to the public so it will need to be in a private location. This issue covers identifying somewhere suitable.

Follow-up to https://github.com/adoptium/infrastructure/issues/2731

Noting also that at present the images are not being automatically regenerated when the playbooks are updated, which could be a first step that can be done before pushing it externally.