`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.
{
    LogInstance().m_reopen_file = true;
}
#else
static BOOL WINAPI consoleCtrlHandler(DWORD dwCtrlType)
{
    StartShutdown();
    Sleep(INFINITE);
    return true;
}
#endif
#ifndef WIN32
static void registerSignalHandler(int signal, void(*handler)(int))
{
    struct sigaction sa;
    sa.sa_handler = handler;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = 0;
    sigaction(signal, &sa, nullptr);
}
#endif
static boost::signals2::connection rpc_notify_block_change_connection;
static void OnRPCStarted()
{
    rpc_notify_block_change_connection = uiInterface.NotifyBlockTip_connect(std::bind(RPCNotifyBlockChange, std::placeholders::_2));
}
static void OnRPCStopped()