feat: add flash gRPC commands

[MatteoPologruto]

Motivation

Add grpc support for download and flash commands.

Change description

Add grpc support for download and flash commands. The flash progress coming from qdl has not been implemented yet. This is an example of the command's output:

{
  "downloadProgress": {
    "update": {
      "downloaded": "2357118536",
      "totalSize": "2357118536"
    }
  }
}
{
  "downloadProgress": {
    "end": {
      "success": true
    }
  }
}
{
  "extractionProgress": {
    "name": "extract",
    "message": "Start"
  }
}
{
  "extractionProgress": {
    "name": "extract",
    "message": "arduino-unoq-debian-image-20251127-441/disk-sdcard.img.root"
  }
}
{
  "extractionProgress": {
    "name": "extract",
    "completed": true
  }
}
{
  "flashProgress": {
    "name": "flash",
    "message": "Starting"
  }
}
{
  "flashProgress": {
    "name": "flash",
    "completed": true
  }
}

Additional Notes

$ grpcurl \
  -plaintext \
  -import-path ./rpc \
  -proto cc/arduino/flasher/v1/commands.proto \
  -d '{"version": "latest", "temp_path": "<path>", "preserve_user": false}' \
  127.0.0.1:50052 \
  cc.arduino.flasher.v1.Flasher.Flash

Reviewer checklist

• PR addresses a single concern.
• PR title and description are properly filled.
• Changes will be merged in main.
• Changes are covered by tests.
• Logging is meaningful in case of troubleshooting.

[lucarin91]

I think we should add a better object for the extract and flash command

[lucarin91]

Here, I would expect to have something like

Suggested change

	DownloadProgress download_progress = 1;
	// Progress of the extraction.
	TaskProgress extraction_progress = 2;
	// Progress of qdl flashing.
	TaskProgress flash_progress = 3;
	// Download result.
	Result result = 4;
	DownloadProgress download_progress = 1;
	ExtractProgress extraction_progress = 2;
	FlashProgress flash_progress = 3;
	Result result = 4;

each of which has its own internal states

[cmaglie]

This is duplicated code with the Download service. Please, move the duplicated code in a private function that is called from both Download and Flash services.

Moreover, in the Download service, the check for free space is not performed. This will be solved automatically when the duplicated code is factored out.