es_out: fix track infos regression
Regression from
7e719ff464f48cc13977fd54980e28e783612816
Add a missing input_item_UpdateTracksInfo(). Indeed, tracks were updated only
if the format was changed from the decoders (and therefore killed preparsing).
Revert back tracks i_codec to the original demuxer i_codec. Indeed, it seems
that the following statement was a bad idea:
"The fmt of the ES events will now keep the decoder codec. The original codec
from the demuxer is still available via fmt.i_original_fourcc."