ISSUE DESCRIPTION

This is a fix for clients remaining desynchronized from the server when freezing / pausing their games.

When freezing or pausing the game the network-time.gd handles this pause when it detects a large time has elapsed since the last update.

EXPLAINATION

When pausing or freezing the network timers continue to update so our network clock stays synced and our reference clock requires little catchup. However, our _tick variable won't be automatically updated (this is what actually drives the multiplayer).

CONSEQUENCES OF ISSUE

The result is a client who thinks they are in the past, this has two consequences:
The server will interpret the clients inputs as old (older than the max allowed history) and ignore them. The player will then be frozen.
The client will interpret server updates as being in the future and wont run them until its _tick variable has "caught up". The effect is that a client sees server updates with a delay equal to the time frozen/paused.

This does not just resolve itself and currently breaks the client until they disconnect/reconnect.

FIX DESCRIPTION

This commit adds a line which updates the _tick to the current network time after a pause is detected. This PR doesn't clear the rollback buffers and will mean that potentially some client inputs will still be sent with an old _tick (not a big deal as new inputs will now have the updated _tick but it would be nice to add).

I first noticed this issue when I paused by games and noticed my client never "resyncs" with the server, in actuality its clock was synced but its _ticks was not. To reproduce / test this issue our yourself add this code to your game.
I tested this PR by adding it to the player.gd script in the multiplayer-fps example.

func _process(delta: float) -> void:
	if Input.is_key_pressed(KEY_T):
                # Uncomment below to test freezes
		OS.delay_msec(2000)

                # Uncomment below to test pauses
		#get_tree().create_timer(2.0, true, false, true).timeout.connect(get_tree().set_pause.bind(false))
		#get_tree().set_pause(true)

Then create to instances of the fps game, one as host, and other as client. As the client press T and introduce delay until the timer becomes permanently behind and becomes unresponsive.