Add 13.0 job for SAST orchestrator

What does this MR do?

This MR adds a build job to the SAST orchestrator to create a 13-0-stable docker image. While it is true that gitlab-org/gitlab#207128 (closed) will move us away from this behavior, we need to make sure this image is available so we don't break DinD SAST early in the development timeframe of %13.0.

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/security-products/release/-/issues/96

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
  • Job definition example
  • CI Templates (to be removed)
  • Vendored CI Templates (also in CE)
  • Ensure that all of the ENV vars supported are propagated to Docker containers upon docker run in job definitions
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer