Implement Cosign signatures in pipeline

Summary

This issue will cover the actual code changes that need to be made to the pipeline to enable us to use Cosign to sign images in registry.

Changes

• The harbor stage will need to be updated to leverage the cosign binary after the image has been pushed to registry1
  • cosign sign --key awskms:///<tbd prod key id> registry1.dso.mil/ironbank/redhat/ubi/ubi8:8.5