Remove yaml output format from --format flag. / Deprecate --format json in favor of --json

[cmaglie]

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• The PR has no duplicates (please search among the Pull Requests
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• The PR follows
  our contributing guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• UPGRADING.md has been updated with a migration guide (for breaking changes)
• configuration.schema.json updated if new parameters are added.

What kind of change does this PR introduce?

• Removes the yaml option from the --format flag
• Adds a --json flag that is equivalent to --format json
• Hides --format xxxx flag from the help (but the flag is still functional)

What is the current behavior?

$ arduino-cli board list --format json -w
{
  "eventType": "add",
  "port": {
    "address": "/dev/ttyS4",
    "label": "/dev/ttyS4",
    "protocol": "serial",
    "protocol_label": "Serial Port",
    "properties": {}
  }
}
^C
$ arduino-cli board list --format yaml -w
eventType: add              <---- this is an invalid YAML stream
port:
  address: /dev/ttyS4
  label: /dev/ttyS4
  properties: {}
  protocol: serial
  protocol_label: Serial Port

^C

What is the new behavior?

$ arduino-cli board list --format json -w
{
  "eventType": "add",
  "port": {
    "address": "/dev/ttyS4",
    "label": "/dev/ttyS4",
    "protocol": "serial",
    "protocol_label": "Serial Port",
    "properties": {}
  }
}
^C
$ arduino-cli board list --format yaml -w
Invalid output format: yaml
$ arduino-cli board list --json
{
  "detected_ports": [
    {
      "port": {
        "address": "/dev/ttyS4",
        "label": "/dev/ttyS4",
        "protocol": "serial",
        "protocol_label": "Serial Port",
        "properties": {}
      }
    }
  ]
}
$ arduino-cli 
Arduino Command Line Interface (arduino-cli).

Usage:
  arduino-cli [command]

Examples:
  arduino-cli <command> [flags...]

Available Commands:
  board           Arduino board commands.
  burn-bootloader Upload the bootloader.
  cache           Arduino cache commands.
  compile         Compiles Arduino sketches.
  completion      Generates completion scripts
  config          Arduino configuration commands.
  core            Arduino core operations.
  daemon          Run as a daemon on port: 50051
  debug           Debug Arduino sketches.
  help            Help about any command
  lib             Arduino commands about libraries.
  monitor         Open a communication port with a board.
  outdated        Lists cores and libraries that can be upgraded
  sketch          Arduino CLI sketch commands.
  update          Updates the index of cores and libraries
  upgrade         Upgrades installed cores and libraries.
  upload          Upload Arduino sketches.
  version         Shows version number of Arduino CLI.

Flags:
      --additional-urls strings   Comma-separated list of additional URLs for the Boards Manager.
      --config-file string        The custom config file (if not specified the default will be used).
  -h, --help                      help for arduino-cli
      --json                      Print the output in JSON format.
      --log                       Print the logs on the standard output.
      --log-file string           Path to the file where logs will be written.
      --log-format string         The output format for the logs, can be: text, json
      --log-level string          Messages with this level and above will be logged. Valid levels are: trace, debug, info, warn, error, fatal, panic
      --no-color                  Disable colored output.

Use "arduino-cli [command] --help" for more information about a command.

Does this PR introduce a breaking change, and is titled accordingly?

Yes

Other information