Add support for the GHCR build image pushes currently running from sxa's fork

[sxa]

Upstreaming the changes which are used by https://ci.adoptium.net/job/build_image_updater so it's not running off my branch.

Fixes #4047
Part of #3830
Helps progress #4088 which needs to be on top of this.

Checklist

• commit message has one of the standard prefixes
• faq.md updated if appropriate
• other documentation is changed or added (if applicable)
• playbook changes run through VPC or QPC (if you have access)
• VPC/QPC not applicable for this PR
• for inventory.yml changes, bastillion/nagios/jenkins updated accordingly

[sxa]

Note for reviewers - since this is the live version currently in use we should probably merge this as-is to keep it fixed and make any follow-up changes in another PR if needed. Noting that I did have the centos6 parts commented out of the original top level Jenkinsfile but that change in the final commit here should not be relevant for the new Jenkins file.

[steelhead31]

Looks good.