Extend VEX application to container Image scanning

[knqyf263]

Description

At present, Trivy's support for the Vulnerability Exploitability Exchange (VEX) is limited to Software Bill of Materials (SBOM) scanning. It would be beneficial to extend this application to container image scanning, filesystem scanning and other scanning as well.

However, achieving this with the current BOM-Ref approach may not be feasible. Once the experimental implementation of Package URL (PURL) comparison in VEX is completed, it could potentially pave the way for this extension.

The proposed use case for this feature is similar to that of .trivyignore. The key difference is that it would allow us to accomplish the same tasks using VEX, which is a more industry-standard format.