Move files to UI namespace

osu.Game/Graphics/Containers/IExpandingContainer.cs

@@ -0,0 +1,17 @@
+// 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.Framework.Graphics.Containers;
+using osu.Game.Overlays;
+
+namespace osu.Game.Graphics.Containers
+{
+    /// <summary>
+    /// A target expanding container that should be resolved by children <see cref="IExpandable"/>s to propagate state changes.
+    /// </summary>
+    [Cached(typeof(IExpandingContainer))]
+    public interface IExpandingContainer : IContainer, IExpandable
+    {
+    }
+}