Do not regenerate breaks unless meaningful change to object start/end…

… times is detected

Tangentially found when profiling #28792.

For reproduction, import https://osu.ppy.sh/beatmapsets/972#osu/9007,
move any object on the playfield, and observe a half-second freeze
when ending the drag.

osu.Game/Screens/Edit/EditorBeatmapProcessor.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using osu.Game.Beatmaps;
 using osu.Game.Beatmaps.Timing;
@@ -18,6 +19,11 @@ public class EditorBeatmapProcessor : IBeatmapProcessor
 
  private readonly IBeatmapProcessor? rulesetBeatmapProcessor;
 
+ /// <summary>
+ /// Kept for the purposes of reducing redundant regeneration of automatic breaks.
+ /// </summary>
+ private HashSet<(double, double)> objectDurationCache = new HashSet<(double, double)>();
+
  public EditorBeatmapProcessor(EditorBeatmap beatmap, Ruleset ruleset)
  {
  Beatmap = beatmap;
@@ -38,6 +44,13 @@ public void PostProcess()
 
  private void autoGenerateBreaks()
  {
+ var objectDuration = Beatmap.HitObjects.Select(ho => (ho.StartTime, ho.GetEndTime())).ToHashSet();
+
+ if (objectDuration.SetEquals(objectDurationCache))
+ return;
+
+ objectDurationCache = objectDuration;
+
  Beatmap.Breaks.RemoveAll(b => b is not ManualBreakPeriod);
 
  foreach (var manualBreak in Beatmap.Breaks.ToList())