WiFi MAC address is bogus if AP/STA mode has not been yet selected

The mbed driver for 1DX module assigns MAC addresses only later in the process.
Normal Arduino examples will require it to be populated before calling `WiFi.scan()` or any other function that forces STA mode, so the result will be uninitialized memory.

Start by tracing the mbed driver for the 1DX module and how it assigns the MAC address before AP or STA mode is selected. Check the WiFi.scan() path and other functions that force STA mode. Done means the MAC address is populated before those calls can use it, rather than reading uninitialized memory.

Written by the indexing model from the issue text.