Make `load-containers` working with custom `artifactSuffix`

[Frawless]

Currently the load-containers action counts with artifacts called containers-<ARCH>.tar. However, next to it build-containers adds project name into the artifact name via artifactSuffix parameter. We should either:

• add this parameter into load-containers and make it usable for other projects
• remove it and let the projects do it

Currently operators repo has it's own implementation of this action. Drain-cleaner and KAO implements the same as part of run-systemtest actions.