`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.
}
    if (args.GetBoolArg("-listenonion", DEFAULT_LISTEN_ONION)) {
        const auto bind_addr = connOptions.onion_binds.front();
        if (connOptions.onion_binds.size() > 1) {
            InitWarning(strprintf(_("More than one onion bind address is provided. Using %s for the automatically created Tor onion service."), bind_addr.ToStringIPPort()));
        }
        StartTorControl(bind_addr);
    }
    for (const std::string& strBind : args.GetArgs("-whitebind")) {
        NetWhitebindPermissions whitebind;
        bilingual_str error;
        if (!NetWhitebindPermissions::TryParse(strBind, whitebind, error)) return InitError(error);
        connOptions.vWhiteBinds.push_back(whitebind);
    }
    for (const auto& net : args.GetArgs("-whitelist")) {
        NetWhitelistPermissions subnet;
        bilingual_str error;
        if (!NetWhitelistPermissions::TryParse(net, subnet, error)) return InitError(error);
        connOptions.vWhitelistedRange.push_back(subnet);
    }
    connOptions.vSeedNodes = args.GetArgs("-seednode");
     Initiate outbound connections unless connect=0
    connOptions.m_use_addrman_outgoing = !args.IsArgSet("-connect");
    if (!connOptions.m_use_addrman_outgoing) {
        const auto connect = args.GetArgs("-connect");
        if (connect.size() != 1 || connect[0] != "0") {
            connOptions.m_specified_outgoing = connect;
        }
    }
    const std::string& i2psam_arg = args.GetArg("-i2psam", "");