multiqueue: Fix interleave calculation for data before segment start

multiqueue: Fix interleave calculation for data before segment start

This commit modifies the interleave calculation to allow growing when incoming
data is before the segment start.

The rationale is that there is no requirement whatsoever for data before the
segment start to be "coherent" on all streams.

For example, a demuxer could rightfully send data from the video stream from the
previous keyframe (potentially quite a bit before the segment start) and the
audio from just before the segment start.

This will activate the same logic as growing the interleave when some streams
haven't received buffers yet.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1892>