`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.
{
    rpc_notify_block_change_connection.disconnect();
    RPCNotifyBlockChange(nullptr);
    g_best_block_cv.notify_all();
    LogPrint(BCLog::RPC, "RPC stopped.\n");
}
void SetupServerArgs(ArgsManager& argsman)
{
    SetupHelpOptions(argsman);
    argsman.AddArg("-help-debug", "Print help message with debugging options and exit", ArgsManager::ALLOW_ANY, OptionsCategory::DEBUG_TEST); 
    init::AddLoggingArgs(argsman);
    const auto defaultBaseParams = CreateBaseChainParams(CBaseChainParams::MAIN);
    const auto testnetBaseParams = CreateBaseChainParams(CBaseChainParams::TESTNET);
    const auto signetBaseParams = CreateBaseChainParams(CBaseChainParams::SIGNET);
    const auto regtestBaseParams = CreateBaseChainParams(CBaseChainParams::REGTEST);
    const auto defaultChainParams = CreateChainParams(argsman, CBaseChainParams::MAIN);
    const auto testnetChainParams = CreateChainParams(argsman, CBaseChainParams::TESTNET);
    const auto signetChainParams = CreateChainParams(argsman, CBaseChainParams::SIGNET);
    const auto regtestChainParams = CreateChainParams(argsman, CBaseChainParams::REGTEST);
    
    std::vector<std::string> hidden_args = {
        "-dbcrashratio", "-forcecompactdb",
        
        "-choosedatadir", "-lang=<lang>", "-min", "-resetguisettings", "-splash", "-uiplatform"};
    argsman.AddArg("-version", "Print version and exit", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
#if HAVE_SYSTEM
    argsman.AddArg("-alertnotify=<cmd>", "Execute command when a relevant alert is received or we see a really long fork (%s in cmd is replaced by message)", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);