Performance drops when adjusting difficulty settings in editor on an already populated beatmap

[peppy]

This code should only run on mouse release, basically:

osu/osu.Game.Rulesets.Osu/Edit/Setup/OsuDifficultySection.cs

Lines 134 to 148 in b156083

	private void updateValues()
	{
	// for now, update these on commit rather than making BeatmapMetadata bindables.
	// after switching database engines we can reconsider if switching to bindables is a good direction.
	Beatmap.Difficulty.CircleSize = circleSizeSlider.Current.Value;
	Beatmap.Difficulty.DrainRate = healthDrainSlider.Current.Value;
	Beatmap.Difficulty.ApproachRate = approachRateSlider.Current.Value;
	Beatmap.Difficulty.OverallDifficulty = overallDifficultySlider.Current.Value;
	Beatmap.Difficulty.SliderMultiplier = baseVelocitySlider.Current.Value;
	Beatmap.Difficulty.SliderTickRate = tickRateSlider.Current.Value;
	Beatmap.BeatmapInfo.StackLeniency = stackLeniency.Current.Value;
	Beatmap.UpdateAllHitObjects();
	Beatmap.SaveState();
	}