`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.
{
    try {
        CHashVerifier<Stream> verifier(&stream);
        
        unsigned char pchMsgTmp[4];
        verifier >> pchMsgTmp;
        
        if (memcmp(pchMsgTmp, Params().MessageStart(), sizeof(pchMsgTmp)))
            return error("%s: Invalid network magic number", __func__);
        
        verifier >> data;
        
        if (fCheckSum) {
            uint256 hashTmp;
            stream >> hashTmp;
            if (hashTmp != verifier.GetHash()) {
                return error("%s: Checksum mismatch, data corrupted", __func__);
            }
        }
    }
    catch (const std::exception& e) {
        return error("%s: Deserialize or I/O error - %s", __func__, e.what());
    }
    return true;
}
template <typename Data>
bool DeserializeFileDB(const fs::path& path, Data& data, int version)