`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.
script_threads += GetNumCores();
    }
    
    script_threads = std::max(script_threads - 1, 0);
    
    script_threads = std::min(script_threads, MAX_SCRIPTCHECK_THREADS);
    LogPrintf("Script verification uses %d additional threads\n", script_threads);
    if (script_threads >= 1) {
        g_parallel_script_checks = true;
        StartScriptCheckWorkerThreads(script_threads);
    }
    assert(!node.scheduler);
    node.scheduler = std::make_unique<CScheduler>();
    
    node.scheduler->m_service_thread = std::thread(util::TraceThread, "scheduler", [&] { node.scheduler->serviceQueue(); });
    
    node.scheduler->scheduleEvery([]{
        RandAddPeriodic();
    }, std::chrono::minutes{1});
    GetMainSignals().RegisterBackgroundSignalScheduler(*node.scheduler);
    /* Register RPC commands regardless of -server setting so they will be
     * available in the GUI RPC console even if external calls are disabled.
     */
    RegisterAllCoreRPCCommands(tableRPC);
    for (const auto& client : node.chain_clients) {
        client->registerRpcs();
    }
#if ENABLE_ZMQ