splitmuxsink: More fix up for timecode based split
tests: splitmux: Add test for timecode based split
splitmuxsink: Split fragment only if queued time is larger than threshold
The queued time includes the duration of the last queued frame
(i.e., new keyframe) so the condition check should not be inclusive.
Note that the new fragment will be cut excluding the last frame
and therefore if the condition is inclusive way,
the fragment might have one frame shorter duration for all keyframe
stream such as jpeg or all-inter video streams.
splitmuxsink: Don't need to trace next timecode for split decision
Since the commit 94bb76b6b9c48981d3ad42a8c4370b9658db4229, splitmuxsink
will split fragments based on queued time and the threshold of that.
So don't need to store the next timecode for split decision.