Add Portenta boards to Compile Examples CI workflow

[per1234]

Compile library examples for Arduino Portenta H7's M4 and M7 cores during CI run.

The workflow is configured to use the version of the Arduino mbed-Enabled Boards platform from the tip of the default branch of the ArduinoCore-mbed repository. This is necessary because compiling for the Portenta H7 M4 core board fails when using the current release version of the platform (1.2.2). The issue has been fixed (arduino/ArduinoCore-mbed#33), so the second commit of this PR can be reverted after the next release of the Arduino mbed-Enabled Boards platform.

Fixes #180

[github-actions]

Memory usage change @ 24edb4b

Board	flash	RAM for global variables
arduino-beta:mbed:envie_m4	0 - 0	0 - 0
arduino-beta:mbed:envie_m7	0 - 0	0 - 0
arduino:samd:mkr1000	0 - 0	0 - 0
arduino:samd:mkrgsm1400	0 - 0	0 - 0
arduino:samd:mkrnb1500	0 - 0	0 - 0
arduino:samd:mkrwan1300	0 - 0	0 - 0
arduino:samd:mkrwifi1010	0 - 0	0 - 0
arduino:samd:nano_33_iot	0 - 0	0 - 0
esp8266:esp8266:huzzah	0 - 0	0 - 0

Click for full report table

Board	examples/ArduinoIoTCloud-Advanced flash	examples/ArduinoIoTCloud-Advanced RAM for global variables	examples/ArduinoIoTCloud-Basic flash	examples/ArduinoIoTCloud-Basic RAM for global variables	examples/utility/ArduinoIoTCloud_Travis_CI flash	examples/utility/ArduinoIoTCloud_Travis_CI RAM for global variables	examples/utility/Provisioning flash	examples/utility/Provisioning RAM for global variables
arduino-beta:mbed:envie_m4	0	0	0	0	0	0	0	0
arduino-beta:mbed:envie_m7	0	0	0	0	0	0	0	0
arduino:samd:mkr1000	0	0	0	0	0	0	0	0
arduino:samd:mkrgsm1400	0	0	0	0	0	0	0	0
arduino:samd:mkrnb1500	0	0	0	0	0	0	0	0
arduino:samd:mkrwan1300	0	0	0	0	0	0
arduino:samd:mkrwifi1010	0	0	0	0	0	0	0	0
arduino:samd:nano_33_iot	0	0	0	0	0	0	0	0
esp8266:esp8266:huzzah	0	0	0	0	0	0

Click for full report CSV

Board,examples/ArduinoIoTCloud-Advanced<br>flash,examples/ArduinoIoTCloud-Advanced<br>RAM for global variables,examples/ArduinoIoTCloud-Basic<br>flash,examples/ArduinoIoTCloud-Basic<br>RAM for global variables,examples/utility/ArduinoIoTCloud_Travis_CI<br>flash,examples/utility/ArduinoIoTCloud_Travis_CI<br>RAM for global variables,examples/utility/Provisioning<br>flash,examples/utility/Provisioning<br>RAM for global variables
arduino-beta:mbed:envie_m4,0,0,0,0,0,0,0,0
arduino-beta:mbed:envie_m7,0,0,0,0,0,0,0,0
arduino:samd:mkr1000,0,0,0,0,0,0,0,0
arduino:samd:mkrgsm1400,0,0,0,0,0,0,0,0
arduino:samd:mkrnb1500,0,0,0,0,0,0,0,0
arduino:samd:mkrwan1300,0,0,0,0,0,0,,
arduino:samd:mkrwifi1010,0,0,0,0,0,0,0,0
arduino:samd:nano_33_iot,0,0,0,0,0,0,0,0
esp8266:esp8266:huzzah,0,0,0,0,0,0,,

[aentinger]

LGTM 👍 Thank you @per1234 🚀