The ping/pong orders are replaced with a dedicated
(and much smaller) Ping packet that is handled
directly in the client and server Connection wrappers.
This allows clients to respond when the orders are
processed, instead of queuing the pong order to be
sent in the next frame (which added an extra 120ms
of unwanted latency).
The ping frequency has been raised to 1Hz, and pings
are now routed through the server events queue in
preparation for the future dynamic latency system.
The raw ping numbers are no longer sent to clients,
the server instead evaluates a single ConnectionQuality
value that in the future may be based on more than
just the ping times.
* EchoConnection is now a trivial buffer that stores
and repeats orders directly without serialization.
* NetworkConnection no longer subclasses EchoConnection,
and now also caches local orders without serialization.
* Replay recording was moved to NetworkConnection
(it is never used on EchoConnection).
This greatly improves performance by not syncing the world state for every single order processed as this becomes very expensive, at the cost of being unable to directly pinpoint the order that causes a desync. Instead the granularity of detecting desyncs is reduced to the tick level.
