Add comprehensive security tests for quota management and relay functionality

- Introduced `relay_dual_lock_race_harness_security_tests.rs` to validate user liveness during lock hold and release cycles.
- Added `relay_quota_extended_attack_surface_security_tests.rs` to cover various quota scenarios including positive, negative, edge cases, and adversarial conditions.
- Implemented `relay_quota_lock_eviction_lifecycle_tdd_tests.rs` to ensure proper eviction of stale entries and lifecycle management of quota locks.
- Created `relay_quota_lock_eviction_stress_security_tests.rs` to stress test the eviction mechanism under high churn conditions.
- Enhanced `relay_quota_lock_pressure_adversarial_tests.rs` to verify reclaiming of unreferenced entries after explicit eviction.
- Developed `relay_quota_retry_allocation_latency_security_tests.rs` to benchmark and validate latency and allocation behavior under contention.

src/proxy/tests/client_security_tests.rs

@@ -8,7 +8,7 @@ use crate::proxy::handshake::HandshakeSuccess;
 use crate::stream::{CryptoReader, CryptoWriter};
 use crate::transport::proxy_protocol::ProxyProtocolV1Builder;
 use rand::rngs::StdRng;
-use rand::RngCore;
+use rand::Rng;
 use rand::SeedableRng;
 use std::net::Ipv4Addr;
 use tokio::io::{AsyncReadExt, AsyncWriteExt, duplex};