Add stress testing for quota-lock and refactor test guard usage

src/proxy/tests/relay_quota_wake_liveness_regression_tests.rs

@@ -18,10 +18,8 @@ fn saturate_lock_cache() -> Vec<Arc<std::sync::Mutex<()>>> {
     retained
 }
 
-fn quota_test_guard() -> std::sync::MutexGuard<'static, ()> {
-    super::quota_user_lock_test_guard()
-        .lock()
-        .unwrap_or_else(|poisoned| poisoned.into_inner())
+fn quota_test_guard() -> impl Drop {
+    super::quota_user_lock_test_scope()
 }
 
 #[tokio::test]