Perf/snapshot bench overhead

[Agbasimere]

Closes: #1021

Description

This PR addresses the performance tracking of the Soroban simulator's snapshot mechanism. It introduces a comprehensive benchmark to ensure that loading ledger snapshots (which populate the Host storage) does not degrade core simulation performance beyond acceptable limits.

Key Changes

• Benchmark Suite: Added simulator/benches/snapshot_bench.rs using criterion.
• Performance Measurement:
  • Compares execution time of a baseline Host (no snapshots) against a Host populated with 1,000 ledger entries.
  • Measures the cost of 1,000 host function calls to detect any regression in core simulation logic.
• Reporting: Configured criterion with csv_output for tracking results over time.
• CI Integration: Updated .github/workflows/ci.yml to run cargo bench -- --test to prevent regressions during the build process.
• Crate Visibility: Made runner public in lib.rs to allow the benchmark harness to initialize the simulation environment.

Acceptance Criteria

• Benchmarks added in simulator/benches/snapshot_bench.rs.
• Comparison of 1,000 host functions with vs without snapshots.
• Results exportable to CSV.
• Automated run in CI.

File Changes

• simulator/Cargo.toml: Added criterion and [[bench]] section.
• simulator/benches/snapshot_bench.rs: Native Rust performance benchmark implementation.
• simulator/src/lib.rs: Exposed runner module for benchmarking.
• .github/workflows/ci.yml: Added benchmark verification step.

Testing

Ran baseline benchmark locally:

cd simulator
cargo bench --bench snapshot_bench

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[dotandev]

fix ci and conflicts.

[Agbasimere]

@dotandev All checks passed, Kindly merge.