fix(nargo): include validation policy in artifact cache reuse

[1sgtpepper]

Problem Resolved

Resolves #12843

Summary of Changes

Prevents a compile from reusing a program artifact produced with incompatible compilation or validation options. The existing artifact hash now covers the monomorphized program and every option that can affect the persisted artifact or cached diagnostics.

This keeps the fix inside the cache owner and adds no artifact field or serialization surface; artifacts carrying the old source-only hash naturally miss once and are rebuilt. Diagnostic-only modes that need fresh output force compilation without becoming persistent identity. End-to-end nargo compile regressions prove that default validation is rerun after both checks were skipped and that cached compilation warnings are reevaluated when warning policy changes.

User Documentation

Check one:

• No user documentation needed.
• Documented in docs/.
• [For Experimental Features] Documentation tracking issue created:

PR Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

Validation:

• cargo test -p noirc_artifacts --lib
• cargo test -p noirc_driver --lib
• cargo test -p nargo_cli --test compile_cache
• cargo check -p nargo
• cargo clippy -p noirc_driver -p noirc_artifacts --lib -- -D warnings
• cargo clippy -p nargo_cli --test compile_cache -- -D warnings
• cargo fmt --check

[github-actions]

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