`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.
RegisterValidationInterface(g_zmq_notification_interface);
    }
#endif
    
    fReindex = args.GetBoolArg("-reindex", false);
    bool fReindexChainState = args.GetBoolArg("-reindex-chainstate", false);
    
    int64_t nTotalCache = (args.GetArg("-dbcache", nDefaultDbCache) << 20);
    nTotalCache = std::max(nTotalCache, nMinDbCache << 20); 
    nTotalCache = std::min(nTotalCache, nMaxDbCache << 20); 
    int64_t nBlockTreeDBCache = std::min(nTotalCache / 8, nMaxBlockDBCache << 20);
    nTotalCache -= nBlockTreeDBCache;
    int64_t nTxIndexCache = std::min(nTotalCache / 8, args.GetBoolArg("-txindex", DEFAULT_TXINDEX) ? nMaxTxIndexCache << 20 : 0);
    nTotalCache -= nTxIndexCache;
    int64_t filter_index_cache = 0;
    if (!g_enabled_filter_types.empty()) {
        size_t n_indexes = g_enabled_filter_types.size();
        int64_t max_cache = std::min(nTotalCache / 8, max_filter_index_cache << 20);
        filter_index_cache = max_cache / n_indexes;
        nTotalCache -= filter_index_cache * n_indexes;
    }
    int64_t nCoinDBCache = std::min(nTotalCache / 2, (nTotalCache / 4) + (1 << 23)); 
    nCoinDBCache = std::min(nCoinDBCache, nMaxCoinsDBCache << 20); 
    nTotalCache -= nCoinDBCache;
    int64_t nCoinCacheUsage = nTotalCache; 
    int64_t nMempoolSizeMax = args.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
    LogPrintf("Cache configuration:\n");
    LogPrintf("* Using %.1f MiB for block index database\n", nBlockTreeDBCache * (1.0 / 1024 / 1024));
    if (args.GetBoolArg("-txindex", DEFAULT_TXINDEX)) {
        LogPrintf("* Using %.1f MiB for transaction index database\n", nTxIndexCache * (1.0 / 1024 / 1024));