Previously they were stored inline inside a GArray, but as references to the tracks were stored in various other places although the array could still be updated (and reallocated!), this could lead to dangling references in various places. Instead now store them in a GPtrArray in their own allocation so each track's memory position stays fixed. Fixes ZDI-CAN-22299 Fixes https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/3055 Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5635>
