ci(scorecard): fix missing image tags

[tthvo]

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Related to #609

Description of the change:

• Fixed missing scorecard image tags while pushing to ghcr.io.
• Also, refactor image tag computing into a separate for the scorecard-test job. This eases future refactoring when we implements /build_test command here.
  • CI tag: ci-${COMMIT_SHA}
  • Pull Request Tag: pr-${PR _NUMBER}-${COMMIT_SHA}

Motivation for the change:

CI Fail: https://github.com/cryostatio/cryostat-operator/actions/runs/6004320255/job/16284655157

[tthvo]

Sample run:

• Push: https://github.com/tthvo/cryostat-operator/actions/runs/6010595391
• Pull Request: https://github.com/tthvo/cryostat-operator/actions/runs/6010599404/job/16302354824?pr=7