List boards with cpu option in FQBN

[brusherru]

Enhancement request

It will be handy to get a cpu option in FQBN while listing boards (or listing all boards) as a subset.

When listing all boards:

...
Arduino/Genuino Mega or Mega 2560		arduino:avr:mega
↳ ATmega 2560 (Mega 2560)			arduino:avr:mega:cpu=atmega2560
↳ ATmega 1280					arduino:avr:mega:cpu=atmega1280
...

When listing connected boards:

FQBN                	  		Port                  	ID         	Board Name      
arduino:avr:mega2560			/dev/cu.usbmodem1411	2341:0042	Arduino/Genuino Mega or Mega 2560
↳ arduino:avr:mega:cpu=atmega2560						ATmega 2560 (Mega 2560)			
↳ arduino:avr:mega:cpu=atmega1280						ATmega 1280

[brusherru]

It may be turned on with an optional flag --verbose or something like this.

[brusherru]

Oh. I forget that there could be more than one option (E.G. esp8266 have a lot of options).
So I propose to do something like:

{
  fqbn: 'arduino:avr:mega',
  name: 'Arduino/Genuino Mega or Mega 2560',
  options: {
    cpu: [
      {
        value: 'atmega2560',
        name: 'ATmega 2560 (Mega 2560)',
        default: true,
      },
      {
        value: 'atmega1280',
        name: 'ATmega 1280'
      }
    ]
  }
}

And for text output, something like this:

FQBN			Port			ID		Board Name
arduino:avr:mega2560	/dev/cu.usbmodem1411	2341:0042	Arduino/Genuino Mega or Mega 2560
↳ cpu
↳ ↳ Value	Option Name		Default
↳ ↳ atmega2560	ATmega 2560 (Mega2560)	✔
↳ ↳ atmega1280	ATmega 1280

So it could be extended with any amount of options.
Also, we could mark some of options as "default" (additional field default: true or column in text output), if it possible.