`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.
{
    static const auto testing_setup = MakeNoLogFileContext<>();
}
FUZZ_TARGET_INIT(banman, initialize_banman)
{
    
    
    
    int limit_max_ops{300};
    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
    SetMockTime(ConsumeTime(fuzzed_data_provider));
    const fs::path banlist_file = gArgs.GetDataDirNet() / "fuzzed_banlist.dat";
    fs::remove(banlist_file);
    {
        BanMan ban_man{banlist_file, nullptr, ConsumeBanTimeOffset(fuzzed_data_provider)};
        while (--limit_max_ops >= 0 && fuzzed_data_provider.ConsumeBool()) {
            CallOneOf(
                fuzzed_data_provider,
                [&] {
                    ban_man.Ban(ConsumeNetAddr(fuzzed_data_provider),
                                ConsumeBanTimeOffset(fuzzed_data_provider), fuzzed_data_provider.ConsumeBool());
                },
                [&] {
                    ban_man.Ban(ConsumeSubNet(fuzzed_data_provider),
                                ConsumeBanTimeOffset(fuzzed_data_provider), fuzzed_data_provider.ConsumeBool());
                },