net/webrepl: Support LAN interfaces and fix AttributeError on ports without WLAN

[AsinoEsel]

WebREPL currently does not support LAN interfaces, and raises an AttributeError on webrepl.start() on boards without network.WLAN, such as the ESP32-P4 port. The exception is raised in setup_conn() in line 105:

    for i in (network.WLAN.IF_AP, network.WLAN.IF_STA):

Steps to reproduce:

1. Flash the latest firmware for the ESP32-P4 port
2. Inside the REPL, configure WebREPL using import webrepl_setup
3. If configured to enable on startup, it will immediately raise:

  File "<stdin>", line 1, in <module>
  File "webrepl.py", line 1, in start
  File "webrepl.py", line 1, in setup_conn
AttributeError: 'module' object has no attribute 'WLAN'

This PR adds

1. a try-except block for the existing WLAN logic, to catch this AttributeError.
2. support for LAN interfaces, with a try-except block to catch errors (such as a TypeError in the event that the LAN interface has not yet been initialized).
3. A fallback for when neither type of interface has been found.

I have tested this on an ESP32-P4-ETH board, and a generic ESP32 board. Works as intended.

This issue was raised before in #920 by @Romaric-RILLET, but that attempted fix failed to cover the network.WLAN AttributeError (as it happens outside the try-except block), making it impossible for ethernet-only boards to use WebREPL.