Synchronize zephyrCommon.cpp with arduino 0.55.0 (Part 2)

[soburi]

Continued from #190.

• Lightweight class

  • Miscellaneous fix
    treewide: fix SPDX tags on existing files #200
    core: Introduce itoa.cpp #202
    core: Fixes for proper core compatibility #203
    core: arduino: add ShiftIn/ShiftOut #204
    core: arduino: add common files for compatibility #205
    feat: import postvariant.h if it exists #207
    variants: Restore removed empty variant.h #213

• Middleweight class

  • Library addition
    CAN: add library and board overlay configuration #194
  • Variant addition (worked with https://github.com/arduino/zephyr/tree/zephyr-arduino-v4.2.0)
    variants: Add community-supported boards #196
    variants: Add new Arduino boards (other than STM32) #197
    variants: Add support for Arduino Uno Q #198
    variants: Add new Arduino boards (STM32 boards) #199

• Heavyweight class

  • Variant update
    variants: import Nano 33 BLE Sense updates from 0.55.0 #201
  • Serial improvement
    core: Improve Serial implements #206
    core: Add variant and loop hooks to Arduino main #212
  • Serial USB
    core: Support SerialUSB #209