A few internal improvements

[mibac138]

Each commit is self-contained and small, so grouping them into a single PR seems reasonable.

[notfood]

Isn't max packet size already handled by LiteNetLib? I remember seeing a similar error before.

[mibac138]

LNL has both a limit for a single packet as well as for packets it internally fragments (here). However, when we fragment the packet ourselves, LNL doesn't know about the whole packet's size and thus it cannot make sure the packet has a reasonable size.
Also, we verify the packet's size when receiving a fragmented packet (here) so I think it makes sense to also verify it ourselves when sending a packet and possibly catching an issue earlier.