The RP2040, Pico SDK and the Pico documentation are all produced by Raspberry Pi ( https://www.raspberrypi.com/ ) and not by Raspberry Pi Foundation ( https://www.raspberrypi.org/ )

This is needed to update the pyRF24 pkg to use latest master.

This does not affect RF24 lib builds because
RF24_NO_IRQ is respected in the root CMakeLists.txt.
But, the pyRF24 pkg doesn't actually use the root CMakeLists.txt.
Instead, the pyRF24 pkg only uses utility/CMakeLists.txt.

Also amends an outdated comment in the definition.

solves #867

Calling this macro caused the following error: 'const void*' is not a pointer-to-object type when defined by another library (in this instance ArduinoJSON)

see bblanchon/ArduinoJson/#1790

See nRF24/RF24Mesh#210
To allow users to configure the PA level in higher layers of the stack, do not set PA level in radio.begin();.

* make other pgm_read_* macros complaint with unified API

Corresponding to #864, this completes compliance with the unified ArduinoCore-API about 

- `pgm_read_word()`
- `pgm_read_byte()`

see https://github.com/arduino/ArduinoCore-API/blob/e26862e453c1234e1c23506d1839bfa68999d911/api/deprecated-avr-comp/avr/pgmspace.h#L102-L103

* add some boards to the Arduino & PIO CI

* run clang-format on changed files


fix param name

* install arduino-pico core in arduino CI

install cpp-linter from PyPI

keep installing AVR, megaAVR, MBED, SAM, & SAMD platforms in addition to arduino-pico

* add printf support to ESP* and arduino-pico cores
* add ESP32/8266 boards to PlatformIO CI

   Arduino CLI seems to have trouble getting the esp* core that
   corresponds to the fqbn prefix