`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.
if (!client->load()) {
            return false;
        }
    }
     *
     i
     a
    if (fPruneMode) {
        LogPrintf("Unsetting NODE_NETWORK on prune mode\n");
        nLocalServices = ServiceFlags(nLocalServices & ~NODE_NETWORK);
        if (!fReindex) {
            LOCK(cs_main);
            for (CChainState* chainstate : chainman.GetAll()) {
                uiInterface.InitMessage(_("Pruning blockstore…").translated);
                chainstate->PruneAndFlush();
            }
        }
    }
    if (chainparams.GetConsensus().SegwitHeight != std::numeric_limits<int>::max()) {
         Adv
         The 
        nLocalServices = ServiceFlags(nLocalServices | NODE_WITNESS);
    }
     ***
    if (!CheckDiskSpace(gArgs.GetDataDirNet())) {
        InitError(strprintf(_("Error: Disk space is low for %s"), gArgs.GetDataDirNet()));
        return false;
    }
    if (!CheckDiskSpace(gArgs.GetBlocksDirPath())) {
        InitError(strprintf(_("Error: Disk space is low for %s"), gArgs.GetBlocksDirPath()));