Use CMC for all of multiplayer

osu.Game/Tests/Visual/MultiplayerTestCase.cs

@@ -0,0 +1,36 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Framework.Allocation;
+using osu.Game.Online.Multiplayer;
+
+namespace osu.Game.Tests.Visual
+{
+    public class MultiplayerTestCase : OsuTestCase
+    {
+        private Room room;
+
+        protected Room Room
+        {
+            get => room;
+            set
+            {
+                if (room == value)
+                    return;
+                room = value;
+
+                if (dependencies != null)
+                    dependencies.Model.Value = value;
+            }
+        }
+
+        private CachedModelDependencyContainer<Room> dependencies;
+
+        protected override IReadOnlyDependencyContainer CreateChildDependencies(IReadOnlyDependencyContainer parent)
+        {
+            dependencies = new CachedModelDependencyContainer<Room>(base.CreateChildDependencies(parent));
+            dependencies.Model.Value = room;
+            return dependencies;
+        }
+    }
+}