[CI] [Tech Debt] Make sure images are also published to SUSE staging registry

[jbiers]

The prometheus-federator image is currently only pushed to Dockerhub. We should also be pushing to SUSE Prime STG registry to make sure QA is able to test the project properly when running Prime images.

[jbiers]

Any releases targeting main or newer branches will now also be deployed to SUSE Pime STG registry