`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.
{
        SetNull();
        nCreateTime = nCreateTimeIn;
    }
    SERIALIZE_METHODS(CBanEntry, obj)
    {
        uint8_t ban_reason = 2; 
        READWRITE(obj.nVersion, obj.nCreateTime, obj.nBanUntil, ban_reason);
    }
    void SetNull()
    {
        nVersion = CBanEntry::CURRENT_VERSION;
        nCreateTime = 0;
        nBanUntil = 0;
    }
};
class CAddrDB
{
private:
    fs::path pathAddr;
public:
    CAddrDB();
    bool Write(const CAddrMan& addr);
    bool Read(CAddrMan& addr);
    static bool Read(CAddrMan& addr, CDataStream& ssPeers);
};
class CBanDB