Add load and stress testing

[ChaoticTempest]

We don't have tests for stress our network to its extreme. By adding these stress tests, we can have more confidence that our network won't just stall out of nowhere or get DDoS'd.

I mentioned this because I just saw this new shiny testing library that integrates into axum: https://github.com/tokio-rs/turmoil

[volovyks]

I will clarify what we need here:

• Load testing. Let's measures our system performance as the workload increases. We need to know what is our maximum number of concurrent users/transactions for each action (new_acc, sign, etc.) and combined.
• Stress/Spike testing. The goal here is to test the system stability. We should give our system more users or transactions that can be handled and make sure that there are no failures and system stays alive and can recover.

[volovyks]

Blocked by: #111