Serial Numbers/UIDs

[peternewman]

I see you've already mentioned this partly in https://github.com/OpenLightingProject/rp2040-dongle/discussions/2 but given it's important we don't get UID clashes in our space so for now if you're using static ones it would be good to switch to some of the reserved ones here (any of the development blocks are fine): https://wiki.openlighting.org/index.php/Open_Lighting_Allocations#UIDs

What serial(s)/MAC(s) does the RP2040 chip ship with and I can suggest some ways we could make use of them based on what we've done in the past.