Add ESP32 Reset Reason to existing pwrmgt.bootreason cli command

[fizzyfuzzle]

This small PR will add the Reset Reason functionality to the pwrmgt.bootreason CLI command for ESP32 based devices. Currently this was implemented for nRF52 devices only.

All the code was already in the current firmware except the ESP32 implementation of the getResetReason() method on the board level.

MeshCore/src/MeshCore.h

Line 74 in 29f0a7f

virtual uint32_t getResetReason() const { return 0; }

This should help with ESP32 boards that have rebooted for unknown reason e.g. during the test of new firmware ;)

Code is copied from https://github.com/IoTThinks/EasySkyMesh, so credits go to @IoTThinks (Thanks for this 👍 )
IoTThinks@f25db3a

[IoTThinks]

Yah, enjoy.

[fizzyfuzzle]

@liamcottle This is a small PR to add the 'reset reason' for ESP32 boards to the pwrmgt.bootreason cli. Would it be possible for this PR to get reviewed?

Thanks in advance!