`banlist.dat` was introduced in https://github.com/bitcoin/bitcoin/pull/6310, storing nodes that were automatically banned (due to exceeding the misbehavior threshold) and manually banned (through the `setban` RPC).

Automatic bans were removed in https://github.com/bitcoin/bitcoin/pull/19219 and replaced with a discouragement filter. That filter is not saved to disk/persisted over shutdown/startup. The `banlist.dat` therefore now only contains addresses that have been banned through the `setban` rpc.

Since https://github.com/bitcoin/bitcoin/pull/15935, we have a specific file for configuration that is updated through the RPC and persisted over shutdown/startup, namely `settings.json`. We should therefore move the manual ban configuration from `banlist.dat` to `settings.json`. Doing so has a couple of benefits:

- `settings.json` is human readable and easily analyzable by any json parser.
- we wouldn't need to maintain custom [de]serialization code for the `banlist.dat` file.

`banlist.dat` is expected to be fairly small and infrequently updated, so disk space/performance are not huge concerns.
{
    SetMockTime(0s); 
    LogInstance().DisconnectTestLogger();
    fs::remove_all(m_path_root);
    gArgs.ClearArgs();
    ECC_Stop();
}
ChainTestingSetup::ChainTestingSetup(const std::string& chainName, const std::vector<const char*>& extra_args)
    : BasicTestingSetup(chainName, extra_args)
{
    
    
    m_node.scheduler = std::make_unique<CScheduler>();
    m_node.scheduler->m_service_thread = std::thread(util::TraceThread, "scheduler", [&] { m_node.scheduler->serviceQueue(); });
    GetMainSignals().RegisterBackgroundSignalScheduler(*m_node.scheduler);
    pblocktree.reset(new CBlockTreeDB(1 << 20, true));
    m_node.fee_estimator = std::make_unique<CBlockPolicyEstimator>();
    m_node.mempool = std::make_unique<CTxMemPool>(m_node.fee_estimator.get(), 1);
    m_node.chainman = std::make_unique<ChainstateManager>();
    
    constexpr int script_check_threads = 2;
    StartScriptCheckWorkerThreads(script_check_threads);
    g_parallel_script_checks = true;
}
ChainTestingSetup::~ChainTestingSetup()