feat: Include scan.primary_identifiers

What does this MR do?

When FP reduction is enabled (Ultimate only), semgrep should now include the exhaustive list of all identifiers for which the scan is running

What are the relevant issue numbers?

gitlab-org/gitlab#368284 (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
• Job definition updated, if necessary
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• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer