Turns GameTicker into an EntitySystem. (#4197)

* GameTicker turned into an EntitySystem

* Turns ClientGameTicker into an EntitySystem, turn NetMessages into events

* Change event names to be more consistent with the rest.

* YAML linter uses the dummy gameticker CVar override.

* Fix game ticker initialization order

* Dummy ticker won't spawn players.

* Fix character creation test

Content.Server/GameTicking/GameTicker.CVars.cs

@@ -0,0 +1,34 @@
+using System;
+using Content.Shared.CCVar;
+using Robust.Shared.ViewVariables;
+
+namespace Content.Server.GameTicking
+{
+    public partial class GameTicker
+    {
+        [ViewVariables]
+        public bool LobbyEnabled { get; private set; } = false;
+
+        [ViewVariables]
+        public bool DummyTicker { get; private set; } = false;
+
+        [ViewVariables]
+        public string ChosenMap { get; private set; } = string.Empty;
+
+        [ViewVariables]
+        public TimeSpan LobbyDuration { get; private set; } = TimeSpan.Zero;
+
+        [ViewVariables]
+        public bool DisallowLateJoin { get; private set; } = false;
+
+        private void InitializeCVars()
+        {
+            _configurationManager.OnValueChanged(CCVars.GameLobbyEnabled, value => LobbyEnabled = value, true);
+            _configurationManager.OnValueChanged(CCVars.GameDummyTicker, value => DummyTicker = value, true);
+            _configurationManager.OnValueChanged(CCVars.GameMap, value => ChosenMap = value, true);
+            _configurationManager.OnValueChanged(CCVars.GameLobbyDuration, value => LobbyDuration = TimeSpan.FromSeconds(value), true);
+            _configurationManager.OnValueChanged(CCVars.GameDisallowLateJoins, invokeImmediately:true,
+                onValueChanged:value => { DisallowLateJoin = value; UpdateLateJoinStatus(); UpdateJobsAvailable(); });
+        }
+    }
+}