`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.
{
    std::string cmd = args.GetArg("-startupnotify", "");
    if (!cmd.empty()) {
        std::thread t(runCommand, cmd);
        t.detach(); 
    }
}
#endif
static bool AppInitServers(NodeContext& node)
{
    const ArgsManager& args = *Assert(node.args);
    RPCServer::OnStarted(&OnRPCStarted);
    RPCServer::OnStopped(&OnRPCStopped);
    if (!InitHTTPServer())
        return false;
    StartRPC();
    node.rpc_interruption_point = RpcInterruptionPoint;
    if (!StartHTTPRPC(&node))
        return false;
    if (args.GetBoolArg("-rest", DEFAULT_REST_ENABLE)) StartREST(&node);
    StartHTTPServer();
    return true;
}
void InitParameterInteraction(ArgsManager& args)