DHCP is enabled by setting the `ip` config entry to "use_dhcp". Reusing this
config field rather than creating a new one means that there is no ambiguity
over which config field takes precedence.
Adds a thread to configure the interface based on DHCP events
Adds a `Dhcpv4Socket` as a wrapper around smoltcp's version
Formalises the storage of the IP addresses so that we can update one in
another module.
There's also a workaround for the first DHCP discover packet frequently
going missing.
Signed-off-by: Michael Birtwell <michael.birtwell@oxionics.com>
