flvdemux: Handle the encoder metadata the same as metadatacreator
flvdemux: Handle the encoder metadata the same as metadatacreator

And store it in our ENCODER tag.

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