`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.
#include <arith_uint256.h>
#include <banman.h>
#include <chainparams.h>
#include <net.h>
#include <net_processing.h>
#include <pubkey.h>
#include <script/sign.h>
#include <script/signingprovider.h>
#include <script/standard.h>
#include <serialize.h>
#include <test/util/net.h>
#include <test/util/setup_common.h>
#include <txorphanage.h>
#include <util/string.h>
#include <util/system.h>
#include <util/time.h>
#include <validation.h>
#include <array>
#include <stdint.h>
#include <boost/test/unit_test.hpp>
static CService ip(uint32_t i)