feat: Allow --config strings in sketch.yaml (esp. baudrate)

[egnor]

Describe the request

It would be nice if sketch.yaml let one specify the default baudrate for arduino-cli monitor, as 9600 baud is v...e...r...y...s...l...o...w... and typing -c baudrate=115200 gets old. Obviously I can make a script wrapper or alias or something but I feel like this kind of thing is what profiles are all about.

(Per #2554 this should probably be per-profile, not sketch-global.)

Describe the current behavior

There's no (obvious) way to specify serial monitor baud rate (or other communications port properties) except on the command line.

Arduino CLI version

1.0.0

Operating system

Linux, N/A

Operating system version

(true in all OS)

Additional context

No response

Issue checklist

• I searched for previous requests in the issue tracker
• I verified the feature was still missing when using the nightly build
• My request contains all necessary details