Added libraries .development flag detection

[cmaglie]

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What kind of change does this PR introduce?

Adds the reporting of a library "in-development" status in the gRPC and JSON output.
The "in-development" status is determined by the presence of a .development file in the library's root directory.

What is the current behavior?

the library "in_development" status is not reported:

$ touch /home/megabug/Arduino/libraries/Robot_Motor/.development
$ arduino-cli lib list "Robot Motor" --format json
[
  {
    "library": {
      "name": "Robot Motor",
      "author": "Arduino",
      "maintainer": "Arduino \u003cinfo@arduino.cc\u003e",
      "sentence": "Enables easy access to the motors of the Arduino Robot Motor board. For Arduino Robot only.",
      "website": "http://www.arduino.cc/en/Reference/RobotLibrary",
      "category": "Device Control",
      "architectures": [
        "avr"
      ],
      "install_dir": "/home/megabug/Arduino/libraries/Robot_Motor",
      "source_dir": "/home/megabug/Arduino/libraries/Robot_Motor/src",
      "version": "1.0.3",
      "license": "Unspecified",
      "location": 1,
      "layout": 1,
      "examples": [
        "/home/megabug/Arduino/libraries/Robot_Motor/examples/Robot_IR_Array_Test",
        "/home/megabug/Arduino/libraries/Robot_Motor/examples/Robot_Motor_Core"
      ],
      "provides_includes": [
        "ArduinoRobotMotorBoard.h",
        "EasyTransfer2.h",
        "LineFollow.h",
        "Multiplexer.h"
      ]
    }
  }
]

What is the new behavior?

The library's "in-development" status is reported:

$ touch /home/megabug/Arduino/libraries/Robot_Motor/.development
$ arduino-cli lib list "Robot Motor" --format json
[
  {
    "library": {
      "name": "Robot Motor",
      "author": "Arduino",
      "maintainer": "Arduino \u003cinfo@arduino.cc\u003e",
      "sentence": "Enables easy access to the motors of the Arduino Robot Motor board. For Arduino Robot only.",
      "website": "http://www.arduino.cc/en/Reference/RobotLibrary",
      "category": "Device Control",
      "architectures": [
        "avr"
      ],
      "install_dir": "/home/megabug/Arduino/libraries/Robot_Motor",
      "source_dir": "/home/megabug/Arduino/libraries/Robot_Motor/src",
      "version": "1.0.3",
      "license": "Unspecified",
      "location": 1,
      "layout": 1,
      "examples": [
        "/home/megabug/Arduino/libraries/Robot_Motor/examples/Robot_IR_Array_Test",
        "/home/megabug/Arduino/libraries/Robot_Motor/examples/Robot_Motor_Core"
      ],
      "provides_includes": [
        "ArduinoRobotMotorBoard.h",
        "EasyTransfer2.h",
        "LineFollow.h",
        "Multiplexer.h"
      ],
      "in_development": true                  <------------
    }
  }
]

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

No

[per1234]

Thanks Cristian!