`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.
}
    for (BlockFilterType filter_type : g_enabled_filter_types) {
        LogPrintf("* Using %.1f MiB for %s block filter index database\n",
                  filter_index_cache * (1.0 / 1024 / 1024), BlockFilterTypeName(filter_type));
    }
    LogPrintf("* Using %.1f MiB for chain state database\n", nCoinDBCache * (1.0 / 1024 / 1024));
    LogPrintf("* Using %.1f MiB for in-memory UTXO set (plus up to %.1f MiB of unused mempool space)\n", nCoinCacheUsage * (1.0 / 1024 / 1024), nMempoolSizeMax * (1.0 / 1024 / 1024));
    bool fLoaded = false;
    while (!fLoaded && !ShutdownRequested()) {
        const bool fReset = fReindex;
        auto is_coinsview_empty = [&](CChainState* chainstate) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
            return fReset || fReindexChainState || chainstate->CoinsTip().GetBestBlock().IsNull();
        };
        bilingual_str strLoadError;
        uiInterface.InitMessage(_("Loading block index…").translated);
        do {
            const int64_t load_block_index_start_time = GetTimeMillis();
            try {
                LOCK(cs_main);
                chainman.InitializeChainstate(*Assert(node.mempool));
                chainman.m_total_coinstip_cache = nCoinCacheUsage;
                chainman.m_total_coinsdb_cache = nCoinDBCache;
                UnloadBlockIndex(node.mempool.get(), chainman);
                 
                 
                pblocktree.reset();
                pblocktree.reset(new CBlockTreeDB(nBlockTreeDBCache, false, fReset));
                if (fReset) {
                    pblocktree->WriteReindexing(true);