use testing setup mempool in ComplexMemPool bench

src/bench/mempool_stress.cpp

@@ -88,7 +88,7 @@ static void ComplexMemPool(benchmark::Bench& bench)
     }
     std::vector<CTransactionRef> ordered_coins = CreateOrderedCoins(det_rand, childTxs, /*min_ancestors=*/1);
     const auto testing_setup = MakeNoLogFileContext<const TestingSetup>(CBaseChainParams::MAIN);
-    CTxMemPool pool;
+    CTxMemPool& pool = *testing_setup.get()->m_node.mempool;
     LOCK2(cs_main, pool.cs);
     bench.run([&]() NO_THREAD_SAFETY_ANALYSIS {
         for (auto& tx : ordered_coins) {