gst/mxf/: Remove the concept of "final" metadata, broken files have updated metadata...

gst/mxf/: Remove the concept of "final" metadata, broken files have updated metadata in following partitions even if ...

Original commit message from CVS:
* gst/mxf/mxfdemux.c: (gst_mxf_demux_reset_metadata),
(gst_mxf_demux_handle_primer_pack),
(gst_mxf_demux_handle_metadata_preface),
(gst_mxf_demux_handle_header_metadata_resolve_references),
(gst_mxf_demux_choose_package),
(gst_mxf_demux_handle_header_metadata_update_streams),
(gst_mxf_demux_parse_footer_metadata),
(gst_mxf_demux_handle_klv_packet):
* gst/mxf/mxfdemux.h:
* gst/mxf/mxftypes.h:
Remove the concept of "final" metadata, broken files have updated
metadata in following partitions even if the current partition
is closed and complete.
If there's a second primer pack inside a partition ignore the second
one instead of throwing an error.
Store the type of a track (audio, video, timestamp, ...) inside the
track struct.
Post no-more-pads only once for a stream and not a second time
when switching the currently playing package.
When updating all streams make sure that we could select and find
a package instead of dereferencing NULL.
Allow descriptive metadata inside metadata parts of a file when
pulling the footer metadata too.
Only switch the currently playing package if a new one was chosen
and the metadata is in a resolved state. If the latter isn't true
postpone the switch until the metadata is resolved.
Pull the footer metadata directly after parsing the header partition
pack if it's not closed or not complete instead of waiting until
the next KLV packet.