gstreamer: rank: Do not implement gst::Rank as enum
Rank is not limited to known types like GST_RANK_NONE, GST_RANK_MARGINAL, GST_RANK_SECONDARY and GST_RANK_PRIMARY, but it can be whatever arbitrary number.
Check for example:
$ gst-inspect-1.0 -a | grep Rank | grep "\+" | head
aacparse: Rank primary + 1 (257)
ac3parse: Rank primary + 1 (257)
amrparse: Rank primary + 1 (257)
dcaparse: Rank primary + 1 (257)
flacparse: Rank primary + 1 (257)
mpegaudioparse: Rank primary + 2 (258)
sbcparse: Rank primary + 1 (257)
wavpackparse: Rank primary + 1 (257)
vp8alphadecodebin: Rank primary + 10 (266)
vp9alphadecodebin: Rank primary + 10 (266)
Edited by Fabián Orccón