IPv6 prefix delegation for subnets

Description

In a use case where we have native IPv6 connectivity in the network we should check for the possibility of prefix delegation as one of the first steps.

Sending out a probe to ask for a prefix and, if succeeded, configure them for the various subnets (e.g. wifi, thread) to fit with the range we got.

This will involve testing out different implementations to get the prefix and distribute it further. Tools like radvd, wide-dhcpd, systemd-networkd, dhcpd, isc-dhcp-client and maybe more will need to be checked to match our needs, packaging status in Yocto, etc.

• Request IPv6 prefix delegation from upstream (eth0, wlan0) and distribute further to subnets
• If now prefix delegation is available, select local prefix and distribute to subnets