tests: qtdemux: test correct pad names are created
tests: qtdemux: test correct pad names are created

Test correct pad names are created in accordance to their media type
in mss mode.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/628>

GStreamer/gst-plugins-good,GStreamer/gst-plugins-good,GStreamer/gst-plugins-good,GStreamer/gst-plugins-good