qtdemux: Move multiview caps calculations, add half-aspect heuristics
qtdemux: Move multiview caps calculations, add half-aspect heuristics

Move the multiview caps calculations to the configure_stream()
function, so the rest of the video info is available, and
use the gst_video_multiview_guess_half_aspect() function to
determine if the half-aspect flag should be set on frame-packed
video.

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