Added net performance graphs to MPClientList UI

[ohlidalp]

This is a spinoff from https://github.com/RigsOfRods/rigs-of-rods/pull/3055 Requires updated rorserver - see https://github.com/RigsOfRods/ror-server/pull/152

New features:

• Added send timestamp to RoRnet::Header - all packets now track their time shift between remote client and local client. Note that the existing truck time shift tracking made by Ulteq is unchanged for now.
• Added queue timestamp to RoRnet::Header - all packets now track the delay between creating the packet and transmitting it to server.
• Added recv queue timestamp to NetRecvPacket - all packets now track local delay between receiving packet and processing it.
• Added 3 new graphs to the MPClientList UI: 1. timeshift (should be stable), 2. local recv lag, 3. remote send lag.

Motivation:

• to smoothen out character movement the same way truck movement is smoothed. That requires tracking the timeshift, and Ulteq's truck smoothing code is very much tied to Actor and ActorManager.
• To clean up network timers - there are 3 separate timers (Character, Actor, ActorManager - the pattern is not clear).
• To better understand and tweak network traffic.
• I like diagnostic views.

Time spent: 6.5hours, not counting rorserver.

[ohlidalp]

Closing this as stale and not immediatelly useful - there is a multitude of things waiting to be integrated into RoRnet (tuning, character mods, the teleporting pieces fix) and there are further plans for porting to ENet and adding multiplayer collisions, all of which need to be started clean.