Store test artifacts for a week

What does this MR do?

Stores gl-secret-detection-report.json files generated by the integration-test job for a week. This will aid in debugging test failures and reduces the need to run integration tests locally to update expectation files.

Here it is in action for this MR pipeline:

https://gitlab.com/gitlab-org/security-products/analyzers/secrets/-/jobs/3977518869/artifacts/browse/tmp/test-48863/custom_ruleset_config/running-image-with-test-project-with-custom-rulesets-with-file-passthrough-behaves-like-successful-scan-creates-a-report/

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added
• If you are adding a new rule, a link to a regex101 example is included in the description
• 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
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer