tests: qtmux: add tests to verify it handles non-0 segments
tests: qtmux: add tests to verify it handles non-0 segments

Both input streams in this test have a segment.start = 10s, so
output should start from 0 anyway.

Another test has both starting at non-0 segments, but the running
time of both streams should still start from 0

ikonst/gst-plugins-good,chamois94/gst-plugins-good,sebras/gst-plugins-good,Kurento/gst-plugins-good,vatavuserban/gst-plugins-good,hizukiayaka/gst-plugins-good,rawoul/gst-plugins-good,chamois94/gst-plugins-good,shelsonjava/gst-plugins-good,stfl/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer__gst-plugins-good,sebras/gst-plugins-good,rawoul/gst-plugins-good,StreamUtils/gst-plugins-good,StreamUtils/gst-plugins-good,pexip/gst-plugins-good,rawoul/gst-plugins-good,froggatt/gst-plugins-good-m,Kurento/gst-plugins-good,kittee/gst-plugins-good,shelsonjava/gst-plugins-good,kittee/gst-plugins-good,GStreamer/gst-plugins-good,pexip/gst-plugins-good,froggatt/gst-plugins-good-m,chamois94/gst-plugins-good,sebras/gst-plugins-good,sebras/gst-plugins-good,shelsonjava/gst-plugins-good,hizukiayaka/gst-plugins-good,pexip/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer__gst-plugins-good,Kurento/gst-plugins-good,kittee/gst-plugins-good,GStreamer/gst-plugins-good,ikonst/gst-plugins-good,stfl/gst-plugins-good,rawoul/gst-plugins-good,froggatt/gst-plugins-good-m,Kurento/gst-plugins-good,chamois94/gst-plugins-good,pexip/gst-plugins-good,GrokImageCompression/gst-plugins-good,ikonst/gst-plugins-good,GrokImageCompression/gst-plugins-good,StreamUtils/gst-plugins-good,Kurento/gst-plugins-good,vatavuserban/gst-plugins-good,froggatt/gst-plugins-good-m,stfl/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer__gst-plugins-good,vatavuserban/gst-plugins-good,stfl/gst-plugins-good,ikonst/gst-plugins-good,GStreamer/gst-plugins-good,pexip/gst-plugins-good,vatavuserban/gst-plugins-good,GrokImageCompression/gst-plugins-good,shelsonjava/gst-plugins-good,hizukiayaka/gst-plugins-good,hizukiayaka/gst-plugins-good,GrokImageCompression/gst-plugins-good,StreamUtils/gst-plugins-good,kittee/gst-plugins-good,GStreamer/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer__gst-plugins-good