`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.
{
private:
    const fs::path m_ban_list_path;
public:
    explicit CBanDB(fs::path ban_list_path);
    bool Write(const banmap_t& banSet);
    bool Read(banmap_t& banSet);
};
/**
 * Dump the anchor IP address database (anchors.dat)
 *
 * Anchors are last known outgoing block-relay-only peers that are
 * tried to re-connect to on startup.
 */
void DumpAnchors(const fs::path& anchors_db_path, const std::vector<CAddress>& anchors);
/**
 * Read the anchor IP address database (anchors.dat)
 *
 * Deleting anchors.dat is intentional as it avoids renewed peering to anchors after
 * an unclean shutdown and thus potential exploitation of the anchor peer policy.
 */
std::vector<CAddress> ReadAnchors(const fs::path& anchors_db_path);
#endif