Rego v1 support & Annotations features

[burdzwastaken]

Rego v1 Support

• Add OPA Rego v1 import/syntax support
• Add --strip-v0-imports flag to strip legacy v0 imports during generation
• Use explicit import list for v1 compatibility
• Add v1 support to custom constraint templates
• Add v1 e2e testing to cron workflow

waiting on upstream plexsystems#665

Annotation Features

• Links() - first-class support for documentation link annotations
• SyncData() - first-class support for syncData annotations (referential constraints)
• Constraints() - support for documenting multiple constraint configurations from a single template
• GetAnnotationOrDefault() - safe annotation access with fallback values

I will make PRs to upstream the other changes