extmod/network_wiznet5k: Add Wiznet Ethernet network interface.

Originally based on both stm32/network_wiznet5k and stm32/modnwwiznet5k.

If MICROPY_PY_LWIP is enabled it uses the LwIP TCP stack in
micropython, communicating with the wiznet controller in MACRAW mode.

If LwIP is not enabled, it runs in modnetwork / socket mode providing
an interface to the TCP stack running on the wiznet controller chip.

Supports defining hw pins in board config or dynamically set at runtime.
Sets a default MAC address in the random namespace from board unique_id.
extmod/network_wiznet5k_provided: Add wiznet ethernet modnetwork driver.

In LwIP mode it supports using the INTN pin from wiznet controller to
receive data from interrupt trigger.

When running in modnetwork mode it includes some modnwwiznet5k updates by
@irinakim12 in micropython#8021, most notably bringing in DHCP support.

Signed-off-by: Andrew Leech <andrew@alelec.net>