lavf/mxfdec: set frame_layout and field_dominance metadata for interlaced j2k streams

Also advice user on how to reconstruct the full frames using joinfields
filter with correct coded field ordered extracted from field dominance.
lavf/mxfdec: add j2k codec to intra only codecs
lavf/mxfdec: generate ptses for interlaced j2k streams

Packet ptses correspond to field number - 1. This plus dividing by a factor
of 2 the stream time base will output correct ptses for decoded frames
since we need 2 packets for one decoded frame.
lavf/mxfdec: fix stream time base for j2k codec with interlaced layout

Since two packets are required to decoded a frame, we need to divide by
a factor of 2 the stream time base so output ptses are correct.
lavf/mxfdec: interpret interlaced j2k sample rate as field rate for some applications

Sample rate should be interpreted as field rate for the files generated
by SAMMA and Canopus systems.