Updated certain events to have more concrete event arguments. Added try-catch block around playlist save logic. Added DispatchQueue where necessary.

Harmonia.Core/Playlists/PlaylistSaveFailedEventArgs.cs

@@ -0,0 +1,7 @@
+namespace Harmonia.Core.Playlists;
+
+public class PlaylistSaveFailedEventArgs(Playlist playlist, Exception exception) : EventArgs
+{
+    public Playlist Playlist { get; } = playlist;
+    public Exception Exception { get; } = exception;
+}