`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.
tx.vin.resize(2777);
        for (unsigned int j = 0; j < tx.vin.size(); j++)
        {
            tx.vin[j].prevout.n = j;
            tx.vin[j].prevout.hash = txPrev->GetHash();
        }
        BOOST_CHECK(SignSignature(keystore, *txPrev, tx, 0, SIGHASH_ALL));
        
        
        for (unsigned int j = 1; j < tx.vin.size(); j++)
            tx.vin[j].scriptSig = tx.vin[0].scriptSig;
        BOOST_CHECK(!orphanage.AddTx(MakeTransactionRef(tx), i));
    }
    
    for (NodeId i = 0; i < 3; i++)
    {
        size_t sizeBefore = orphanage.CountOrphans();
        orphanage.EraseForPeer(i);
        BOOST_CHECK(orphanage.CountOrphans() < sizeBefore);
    }
    
    orphanage.LimitOrphans(40);
    BOOST_CHECK(orphanage.CountOrphans() <= 40);
    orphanage.LimitOrphans(10);
    BOOST_CHECK(orphanage.CountOrphans() <= 10);
    orphanage.LimitOrphans(0);
    BOOST_CHECK(orphanage.CountOrphans() == 0);
}
BOOST_AUTO_TEST_SUITE_END()