Enable use of wired Ethernet modules as first-class LWIP citizens. All
networking classes like MDNS, WebServer, HTTPClient, WiFiClient, and OTA
can use a wired Ethernet adapter just like built-in WiFi.
Two examples updated to show proper use.
Uses the Async Context support built into the Pico SDK. When running on the
Pico it will use the CYW43 async instance.
Uses modified wired Ethernet drivers, thanks Nicholas Humfrey!
Note, the classic, non-LWIP integrated `Ethernet` and related libraries
should still work fine (but not be able to use WebServer/HTTPS/etc.)
Fixes#775
Remove the need to have a separate WiFiClient that's destroyed after
the HTTPClient. Let the object handle its own client, and pass through
any SSL requests.
Also supports the original ::begin methods which need a
WiFiClient(Secure) to be passed in and managed by the app.
