refactor(mhfpacket): rename 15 Unk fields with identified meanings

Replace unknown field names with descriptive names based on handler
logic analysis, switch dispatch patterns, DB query context, and
inline comments:

- ObjectHandleID, IsQuest, ItemIDCount, MaxCount, TokenLength,
  FormatVersion, LogoutType (high confidence from comments/constants)
- QueryType, DataType, MissionIndex, CheckOnly, RequestType,
  ExchangeType, TournamentID (confirmed by handler switch/if usage)

Also fix MsgSysLogout.Build calling ReadUint8 instead of WriteUint8.

network/mhfpacket/msg_parse_large_test.go

@@ -16,7 +16,7 @@ func TestParseLargeMsgSysUpdateRightBuild(t *testing.T) {
 		ClientRespAckHandle: 0x12345678,
 		Bitfield:            0xDEADBEEF,
 		Rights:              nil,
-		UnkSize:             0,
+		TokenLength:             0,
 	}
 
 	bf := byteframe.NewByteFrame()