Both operations now work on coded frame groups (GOPs). This simplifies queueing
of video data. There is rarely any point of dealing with individual video frames
when iterating in DTS order, it's most meaningful to decode or delete whole
coded frame groups at a time, so the sample map will now do that when iterating
by DTS. When iterating in PTS order, the existing behavior is preserved since
that is used for informational purposes, not media processing.
A new private boxed type for coded frame groups was added to provide each data
item to the source buffer. Another possible solution would be creation of a new
GstSample representing the whole group by merging all the samples in a group
into a single sample containing a GstBufferList.
Also, start time filtering was removed from the API since gst_iterator_filter()
can be used by callers to achieve the same result.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8512>
