[breaking] Change gRPC DebugConfigRequest port field type

[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?

Changes gRPC request field type.

• What is the current behavior?

DebugConfigRequest port field has type string.

• What is the new behavior?

DebugConfigRequest port field has now type Port.

// Port represents a board port that may be used to upload or to monitor a board
message Port {
  // Address of the port (e.g., `/dev/ttyACM0`).
  string address = 1;
  // The port label to show on the GUI (e.g. "ttyACM0")
  string label = 2;
  // Protocol of the port (e.g., `serial`, `network`, ...).
  string protocol = 3;
  // A human friendly description of the protocol (e.g., "Serial Port (USB)"
  string protocol_label = 4;
  // A set of properties of the port
  map<string, string> properties = 5;
}```

- **Does this PR introduce a breaking change, and is
[titled accordingly](https://arduino.github.io/arduino-cli/latest/CONTRIBUTING/#breaking)?**

Yes and yes.

* **Other information**:

None.

---

See [how to contribute](https://arduino.github.io/arduino-cli/latest/CONTRIBUTING/)