fix: Ensure Scan.PrimaryIdentifiers has consistent sort

What does this MR do?

By sorting on definition we ensure the slice remains consistent for comparisons.

This should avoid failures such as https://gitlab.com/gitlab-org/security-products/analyzers/report/-/jobs/3057789291, as introduced with !39 (merged)

What are the relevant issue numbers?

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
• Job definition updated, if necessary
  • Auto-DevOps template
  • Job definition example
  • CI Templates
• Ensure the report version matches the equivalent schema version
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer