Updated SongPictureInfo use to async copy of picture data stream. Update other classes accordingly.

Harmonia.Core/Scanner/IAudioFileScanner.cs

@@ -4,6 +4,6 @@ namespace Harmonia.Core.Scanner;
 
 public interface IAudioFileScanner
 {
-    Song[] GetSongs(string[] fileNames);
-    Song[] GetSongsFromPath(string path);
+    Task<Song[]> GetSongsAsync(string[] fileNames, CancellationToken cancellationToken);
+    Task<Song[]> GetSongsFromPathAsync(string path, CancellationToken cancellationToken);
 }