backend tests load: Use reader with Size() method
backend tests load: Use reader with Size() method

fawick/restic,restic/restic,jayme-github/restic,fawick/restic,restic/restic,kurin/restic,ar-jan/restic,middelink/restic,ar-jan/restic,jayme-github/restic,kurin/restic,middelink/restic