Add json output to daemon command

[silvanocerza]

Please check if the PR fulfills these requirements

• The PR has no duplicates (please search among the Pull Requests
  before creating one)
• 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)

• What kind of change does this PR introduce?

Adds json output to an existing command.

• What is the current behavior?

Calling arduino-cli daemon --format json would produce no output.

• What is the new behavior?

Calling arduino-cli daemon --format json now prints the IP and port used:

$ arduino-cli daemon --format json
{
  "IP": "127.0.0.1",
  "Port": "50051"
}

This might be useful when the client lets us choose the port used randomly by setting it to 0:

$ arduino-cli daemon --port 0 --format json 
{
  "IP": "127.0.0.1",
  "Port": "44885"
}

$ arduino-cli daemon --port 0 --format json 
{
  "IP": "127.0.0.1",
  "Port": "33395"
}

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

Nope.

• Other information:

Closes #1583.

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