bench: load test

[kariy]

This PR sets up the foundation for load testing to measure the system’s latency and throughput, with a focus on write performance (i.e. adding transactions).

The long-term goal is to build a suite of performance tests that measure:

• pure TPS/SPS/GPS
• performance of random read-only RPC requests
• combined read + write scenarios

For now, the intended way to perform the test is to run against a Katana with metrics enabled, ideally with Prometheus and Grafana running to monitor the system during the test.

Implementations

• A test database populated with initial state (starting with the Simple example project from the Dojo repo)
• Generating multiple accounts to send parallel transactions
• Basic measurement of:
  • raw TPS (add transactions without estimating fees)
  • accurate TPS (add transactions with fee estimation)

Test scenarios include running Katana both with and without a custom block time.

Future work will expand the test DB with more complex state and introduce read-heavy and mixed load tests.

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Example implementation: https://github.com/kariy/katana-load-test