gst/playback/gstdecodebin2.c: Handle dynamic pads within groups.
Original commit message from CVS: * gst/playback/gstdecodebin2.c: (connect_element), (pad_added_group_cb), (gst_decode_group_check_if_blocked), (sort_end_pads), (gst_decode_group_expose): Handle dynamic pads within groups. Sort pads before exposing them in order to make playbin happy. There still is a race with the multiqueue filling up. This should be solved separately. Fixes #398721