splitmuxsrc: Implement segment query
splitmuxsrc: Implement segment query

Fixes #239

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/713>

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