feat(metrics): add primary link to vulnerability metrics

[kersten]

Description

Add a new primaryLink field to the vulnerability metrics in the collector. This field provides a direct link to the detailed vulnerability information, enhancing the visibility and traceability of vulnerabilities.

This change updates the test cases to include the new primaryLink field in the expected metrics output.

No breaking changes are expected with this addition.

Checklist

• [x] I've read the guidelines for contributing to this repository.
• [x] I've added tests that prove my fix is effective or that my feature works.

[kersten]

@simar7 What do you think about this?