Reduce number of redundant control points displayed on summary timeline

As pointed out in https://github.com/ppy/osu/discussions/16435, beatmaps
with too many control points (usually added via external automation
apps) could cause the lazer editor to grind to a halt.

The overheads here are mostly from the GL side. An eventual goal would
be to render this in a smarter way, rather than using thousands of
drawables. Until that, this optimisation should help reduce the overhead
by omitting control points in close proximity that are redundant for
display purposes.

I've tried to contain this in the display logic directly, with the goal
that it can be ripped out as fast as it was added. Certainly required
more changes than I hoped for, but I don't think it's too ugly.

osu.Game/Screens/Edit/Components/Timelines/Summary/Parts/GroupVisualisation.cs

@@ -1,6 +1,7 @@
 // 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.Linq;
 using osu.Framework.Bindables;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
@@ -23,12 +24,8 @@ namespace osu.Game.Screens.Edit.Components.Timelines.Summary.Parts
 
             Group = group;
             X = (float)group.Time;
-        }
-
-        protected override void LoadComplete()
-        {
-            base.LoadComplete();
 
+            // Run in constructor so IsRedundant calls can work correctly.
             controlPoints.BindTo(Group.ControlPoints);
             controlPoints.BindCollectionChanged((_, __) =>
             {
@@ -60,5 +57,13 @@ namespace osu.Game.Screens.Edit.Components.Timelines.Summary.Parts
                 }
             }, true);
         }
+
+        /// <summary>
+        /// For display purposes, check whether the proposed group is made redundant by this visualisation group.
+        /// </summary>
+        /// <param name="other"></param>
+        /// <returns></returns>
+        public bool IsRedundant(ControlPointGroup other) =>
+            other.ControlPoints.Any(c => InternalChildren.OfType<IControlPointVisualisationRedundant>().Any(c2 => c2.IsRedundant(c)));
     }
 }