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/Presets/PresetSuspicion.cs

@@ -28,7 +28,6 @@ namespace Content.Server.GameTicking.Presets
     public class PresetSuspicion : GamePreset
     {
         [Dependency] private readonly IChatManager _chatManager = default!;
-        [Dependency] private readonly IGameTicker _gameTicker = default!;
         [Dependency] private readonly IRobustRandom _random = default!;
         [Dependency] private readonly IConfigurationManager _cfg = default!;
         [Dependency] private readonly IPrototypeManager _prototypeManager = default!;
@@ -149,7 +148,7 @@ namespace Content.Server.GameTicking.Presets
                 traitor.GreetSuspicion(traitors, _chatManager);
             }
 
-            _gameTicker.AddGameRule<RuleSuspicion>();
+            EntitySystem.Get<GameTicker>().AddGameRule<RuleSuspicion>();
             return true;
         }