Most importantly, this ensures that UDP streams still continue to run even if
they are not linked for a while. With decodebin3 the pads will all be unlinked
unless selected, and selecting a stream at a later time would otherwise switch
to a stream with a stopped udpsrc.
Apart from that this also ensures that actual errors from handling RTP packets
between udpsrc and the source pads are not silently ignored but considered
errors like they would be for TCP/interleaved.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7946>
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