Use recent Trivy features

1. We run Trivy several times in order to generate all report types we need. Instead we could use trivy convert
2. By default Trivy uses a single registry to fetch the trivy-db and trivy-java-db. When rate-limit is reached, Trivy exits with an error code. Instead we could configure Trivy to use multiple registries -> this is being implemented in Trivy directly in this PR, so no need to implement this in TBC