This allows for a port (e.g. esp8266/esp32) to use extmod/modnetwork.c
and provide the globals dict, rather than just a list of interfaces.
When this is used, the default implementation of `network.route` and the
NIC list is not enabled.
Also splits out the LWIP-specific helpers from modnetwork.c into
network_lwip.c.
Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
