`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.
CTxOut output(output_amount, output_destination);
    mempool_txn.vout.push_back(output);
    
    
    FillableSigningProvider keystore;
    keystore.AddKey(input_signing_key);
    
    CCoinsView coins_view;
    CCoinsViewCache coins_cache(&coins_view);
    AddCoins(coins_cache, *input_transaction.get(), input_height);
    
    Coin utxo_to_spend;
    assert(coins_cache.GetCoin(outpoint_to_spend, utxo_to_spend));
    
    std::map<COutPoint, Coin> input_coins;
    input_coins.insert({outpoint_to_spend, utxo_to_spend});
    
    int nHashType = SIGHASH_ALL;
    std::map<int, std::string> input_errors;
    assert(SignTransaction(mempool_txn, &keystore, input_coins, nHashType, input_errors));
    
    if (submit) {
        LOCK(cs_main);
        const MempoolAcceptResult result = AcceptToMemoryPool(m_node.chainman->ActiveChainstate(), *m_node.mempool.get(), MakeTransactionRef(mempool_txn),  false);
        assert(result.m_result_type == MempoolAcceptResult::ResultType::VALID);
    }
    return mempool_txn;
}
TestChain100Setup::~TestChain100Setup()