qtdemux: Specify REDIRECT information in error message

There are in the wild (mp4) streams that basically contain no tracks
but do have a redirect info[0], in which case, we won't be able
to expose any pad (there are no tracks) so we can't post anything but
an error on the bus, as:

- it can't send EOS downstream, it has no pad,
- posting an EOS message will be useless as PAUSED state can't be
  reached and there is no sink in the pipeline meaning GstBin will
  simply ignore it

The approach here is to to add details to the ERROR message with a
`redirect-location` field which elements like playbin handle and use right
away.

[0]: http://movietrailers.apple.com/movies/paramount/terminator-dark-fate/terminator-dark-fate-trailer-2_480p.mov
23 jobs for qtdemux_redirect in 28 minutes and 58 seconds (queued for 9 seconds)
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