Add template for multi container scanner

What does this MR do and why?

Add a new CI template that allows for multi container scanner. It follow similar format to Container-Scanning.latest.gitlab-ci.yml and can be tested via this project.

Key Differences from Existing Template

• Scans multiple container images automatically (vs single image in Container-Scanning.latest.gitlab-ci.yml)
• Uses dynamic pipeline generation via artifacts
• Two-stage process: generation + trigger jobs
• Configurable stages and scanner image version

documentation related MR will be a follow-up to this one.

References

• Related epic: Better support scanning of multiple container i... (gitlab-org#3139) • Zamir Martins • 18.8 • On track
• Related repository: https://gitlab.com/gitlab-org/security-products/analyzers/multiple-container-scanner

Screenshots or screen recordings

Before	After

How to set up and validate locally

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