Feature: Prioritize GPS sync over PTP sync

[Victorsoeby]

I have a system where i have multiple sensors, that need to be time-synchronized. A GNSS receiver is sending PPS pulses and NMEA strings to the LiDAR, that can then timestamp the ROS messages. However, when plug in my camera, it sends PTP data out onto the network. With and unmanaged switch there is currently no way for me to have the LiDAR ignore this data, and use the GNSS data for timesynchronization rather than the PTP data. It would be nice if this was possible to toggle somewhere.