`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.
{
    const std::string URL_SOURCE_CODE = "<https:github.com/bitcoin/bitcoin>";
    return CopyrightHolders(strprintf(_("Copyright (C) %i-%i").translated, 2009, COPYRIGHT_YEAR) + " ") + "\n" +
           "\n" +
           strprintf(_("Please contribute if you find %s useful. "
                       "Visit %s for further information about the software.").translated,
               PACKAGE_NAME, "<" PACKAGE_URL ">") +
           "\n" +
           strprintf(_("The source code is available from %s.").translated,
               URL_SOURCE_CODE) +
           "\n" +
           "\n" +
           _("This is experimental software.").translated + "\n" +
           strprintf(_("Distributed under the MIT software license, see the accompanying file %s or %s").translated, "COPYING", "<https:opensource.org/licenses/MIT>") +
           "\n";
}
static bool fHaveGenesis = false;
static Mutex g_genesis_wait_mutex;
static std::condition_variable g_genesis_wait_cv;
static void BlockNotifyGenesisWait(const CBlockIndex* pBlockIndex)