Add docker digest to documentation.json

Addresses part of #194 (closed)

• buildah push --digestfile=... registry1.dso.mil/ironbank-staging/... to save sha256
• skopeo copy docker://ironbank-staging/ubi8@sha256... docker://ironbank/ubi8:foo
• Add docker://ironbank/ubi8:foo@sha256... to documentation.json

I had to run a full master pipeline in pipeline-test-project, so I made some tweaks to the pipeline to support this. The following variables were set at the pipeline-test-project level:

DOCKER_AUTH_CONFIG_PROD=this is a fake key, never push to prod from pipeline-test-project
REGISTRY_URL=registry1.dsop.io/ironbank-testing
DOCKER_AUTH_CONFIG_TEST (moved from dsop level)

Note, REGISTRY_URL was changed in pipeline-test-project. This variable was always supposed to only be the destination registry path, but it was misused a couple times. I fixed those instances.

Tested in pipeline-test-project/ubi8:
https://repo1.dso.mil/dsop/opensource/pipeline-test-project/ubi8/-/pipelines/126308

• Promoted to ironbank-testing from a sha256
• docker reference included in documentation.json
• Image digest actually matches Harbor finally!
  • !123 (closed) can probably be closed now, the digest matches the image (but the docker archive tar is impossible to make match)