This allows configuring the TTL that is used for multicast packets sent
out on the sockets, and is defaulting to 1 as before. The default might
change at some point.
In some networks multiple hops are needed to reach the PTP clock and
this allows to configure GStreamer in a way that works in such networks.
At a later time, per-domain or per-interface TTL configurations might be
added when needed.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5649>
ba5684d0d7