`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.
{
    std::vector<unsigned char> keydata;
    keydata = g_insecure_rand_ctx.randbytes(32);
    key.Set(keydata.data(), keydata.data() + keydata.size(),  true);
    assert(key.IsValid());
}
BOOST_AUTO_TEST_CASE(DoS_mapOrphans)
{
    
    
    
    
    
    
    g_insecure_rand_ctx = FastRandomContext(ArithToUint256(arith_uint256(33)));
    TxOrphanageTest orphanage;
    CKey key;
    MakeNewKeyWithFastRandomContext(key);
    FillableSigningProvider keystore;
    BOOST_CHECK(keystore.AddKey(key));
    LOCK(g_cs_orphans);
    
    for (int i = 0; i < 50; i++)
    {
        CMutableTransaction tx;
        tx.vin.resize(1);