Emulate report v1

What does this MR do?

Make possible to generate v1 reports using common v2.

This is needed for gitlab-org/security-products/dependency-scanning!44 (merged)

What are the relevant issue numbers?

gitlab-org/gitlab#34853 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added
• [-] Documentation created/updated for GitLab EE, if necessary
• [-] Documentation created/updated for this project, if necessary
• [-] Documentation reviewed by technical writer or follow-up review issue created
• [-] Tests added for this feature/bug
  • See integration test of a branch of Dependency Scanning where uses this branch of common; fails because there's a new advisory, but it behaves as before
  • See integration test of a branch of Dependency Scanning where uses this branch of common, and where the option is enabled; it generates a v1 report (array of vulnerabilities)
• [-] Job definition updated, if necessary
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer