Implement Soroban Rule Benchmark Suite

[mijinummi]

🧠 Concept

Benchmark Soroban analysis rules against sample contracts.

⚠️ Problem

Rule accuracy and performance are difficult to measure consistently.

📁 Implementation Scope

• tests/benchmarks/stellar-rules/

✅ Requirements

• Run benchmark datasets
• Measure detection accuracy
• Measure execution speed

🎯 Acceptance Criteria

• Benchmark suite implemented
• Benchmark reports generated