Add arduino frameworks support for nucleo_wl55jc

[dolfandringa]

This PR fixes issue #552 . It depends on stm32duino/Arduino_Core_STM32#1474 to be merged and included in version 2.1.0 release of Arduino Core STM32. With local forks of that PR and this PR a basic blink sketch compiles, uploads and debugs correctly using the following plaformio.ini and src/main.cpp

[env:stm32wl55]
platform = ststm32
board = nucleo_wl55jc
framework = arduino

#include <Arduino.h>

void setup() {
    pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
    digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
    delay(1000);

}

[dolfandringa]

I did arbitrarily change the version number to 4.3, just because I needed to make sure it was higher.

[dolfandringa]

If anyone needs it, here is the full debug compile of the sketch:
output.txt

[valeros]

Please review my comments above.

[dolfandringa]

Addressed the comments