Drop MatchRuleset terminology completely

osu.Game/Online/Multiplayer/MatchRoomState.cs

@@ -0,0 +1,23 @@
+// 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 System;
+using MessagePack;
+using osu.Game.Online.Multiplayer.MatchTypes.TeamVersus;
+
+#nullable enable
+
+namespace osu.Game.Online.Multiplayer
+{
+    /// <summary>
+    /// Room-wide state for the current match type.
+    /// Can be used to contain any state which should be used before or during match gameplay.
+    /// </summary>
+    [Serializable]
+    [MessagePackObject]
+    [Union(0, typeof(TeamVersusRoomState))]
+    // TODO: this will need to be abstract or interface when/if we get messagepack working. for now it isn't as it breaks json serialisation.
+    public class MatchRoomState
+    {
+    }
+}