feat(test-suite): gw reliable benchmark

[eudelins-zama]

Closes https://github.com/zama-ai/fhevm-internal/issues/449

[Copilot]

Pull Request Overview

This PR implements a reliable benchmarking feature for the gateway stress test tool. The benchmark functionality can run multiple decryption bursts with configurable parameters and collect performance metrics.

• Adds a new benchmark CLI subcommand that takes CSV input files to define test parameters
• Implements statistical analysis (mean, standard deviation) of latency and throughput metrics
• Refactors existing burst functions to return structured performance results instead of just logging

Reviewed Changes

Copilot reviewed 12 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
test-suite/gateway-stress/templates/small_bench.csv	Template CSV file with small benchmark configuration
test-suite/gateway-stress/templates/bench.csv	Template CSV file with comprehensive benchmark configuration
test-suite/gateway-stress/src/main.rs	Adds benchmark module import and subcommand handling
test-suite/gateway-stress/src/decryption/user.rs	Refactors user decryption to return performance metrics
test-suite/gateway-stress/src/decryption/public.rs	Refactors public decryption to return performance metrics
test-suite/gateway-stress/src/decryption/mod.rs	Adds BurstResult struct for performance data
test-suite/gateway-stress/src/cli.rs	Adds benchmark subcommand and arguments structure
test-suite/gateway-stress/src/bench.rs	New module implementing benchmark data structures and statistics
test-suite/gateway-stress/src/app.rs	Implements benchmark execution logic and refactors progress bar initialization
test-suite/gateway-stress/config/config.toml	Updates configuration values for testing
test-suite/gateway-stress/README.md	Documents the new benchmarking functionality
test-suite/gateway-stress/Cargo.toml	Adds csv dependency for benchmark file processing

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[leventdem]

OK!