Localise OrderChanged handling and fix callbacks

The dragged item's position now only updates after the drag finishes. Local handling changes were required to ignore the bindable remove/add events that are fired as a result.

osu.Game/Overlays/Music/PlaylistOverlay.cs

@@ -1,7 +1,6 @@
 // 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 System.Linq;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
@@ -22,12 +21,6 @@ namespace osu.Game.Overlays.Music
         private const float transition_duration = 600;
         private const float playlist_height = 510;
 
-        /// <summary>
-        /// Invoked when the order of an item in the list has changed.
-        /// The second parameter indicates the new index of the item.
-        /// </summary>
-        public Action<BeatmapSetInfo, int> OrderChanged;
-
         private readonly Bindable<WorkingBeatmap> beatmap = new Bindable<WorkingBeatmap>();
         private BeatmapManager beatmaps;
 
@@ -65,7 +58,6 @@ namespace osu.Game.Overlays.Music
                             RelativeSizeAxes = Axes.Both,
                             Padding = new MarginPadding { Top = 95, Bottom = 10, Right = 10 },
                             Selected = itemSelected,
-                            OrderChanged = (s, i) => OrderChanged?.Invoke(s, i)
                         },
                         filter = new FilterControl
                         {