Use LongRunningLoad on network load components

osu.Game/Audio/PreviewTrack.cs

@@ -9,6 +9,7 @@ using osu.Framework.Threading;
 
 namespace osu.Game.Audio
 {
+    [LongRunningLoad]
     public abstract class PreviewTrack : Component
     {
         /// <summary>

osu.Game/Beatmaps/Drawables/BeatmapSetCover.cs

@@ -8,6 +8,7 @@ using osu.Framework.Graphics.Textures;
 
 namespace osu.Game.Beatmaps.Drawables
 {
+    [LongRunningLoad]
     public class BeatmapSetCover : Sprite
     {
         private readonly BeatmapSetInfo set;

osu.Game/Users/Drawables/DrawableAvatar.cs

@@ -13,6 +13,7 @@ using osu.Game.Graphics.Containers;
 
 namespace osu.Game.Users.Drawables
 {
+    [LongRunningLoad]
     public class DrawableAvatar : Container
     {
         /// <summary>