Add SAST IaC to scan execution policies

What does this MR do and why?

Related issue: Enforce IaC Scanning with Scan Execution Polici... (#392966 - closed)

This MR adds yaml support for SAST IaC scan execution policies.

How to set up and validate locally

requires follow-up !112752 (diffs) to enable user-facing change

MR acceptance checklist

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