Integration tests improvements:

1. Added dummy game ticker for future tests to reduce startup time of test. (no loading a map)
2. Re-organized tests a bit.

Content.IntegrationTests/DummyGameTicker.cs

@@ -0,0 +1,67 @@
+using System;
+using System.Collections.Generic;
+using Content.Server.GameTicking;
+using Content.Server.Interfaces.GameTicking;
+using Content.Shared;
+using Robust.Server.Interfaces.Player;
+using Robust.Shared.Timing;
+
+namespace Content.IntegrationTests
+{
+    public class DummyGameTicker : SharedGameTicker, IGameTicker
+    {
+        public GameRunLevel RunLevel { get; } = GameRunLevel.InRound;
+        public event Action<GameRunLevelChangedEventArgs> OnRunLevelChanged;
+
+        public void Initialize()
+        {
+        }
+
+        public void Update(FrameEventArgs frameEventArgs)
+        {
+        }
+
+        public void RestartRound()
+        {
+        }
+
+        public void StartRound()
+        {
+        }
+
+        public void EndRound()
+        {
+        }
+
+        public void Respawn(IPlayerSession targetPlayer)
+        {
+        }
+
+        public void MakeObserve(IPlayerSession player)
+        {
+        }
+
+        public void MakeJoinGame(IPlayerSession player)
+        {
+        }
+
+        public void ToggleReady(IPlayerSession player, bool ready)
+        {
+        }
+
+        public T AddGameRule<T>() where T : GameRule, new()
+        {
+            return new T();
+        }
+
+        public void RemoveGameRule(GameRule rule)
+        {
+        }
+
+        public IEnumerable<GameRule> ActiveGameRules { get; } = Array.Empty<GameRule>();
+
+        public void SetStartPreset(Type type)
+        {
+        }
+    }
+}