add delay mechanism for trivy scan job

[DaMandal0rian]

This PR fixes the trivy scanning workflow, to wait for docker images to be available in github container registry after they are built. The current problem is that when the dispatch event is triggered and trivy runs the scan, the container building jobs have not completed from the Snapshot build workflow, so there are no docker images available in the container registry. A job is added to check if docker images are available first, and when they are the trivy scan container jobs are executed.

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