dev: QT SerialPort may be more convenient than serial port module

[asarhaddon]

Hello. Just in case it has not been discussed yet, the QT framework provides a QTSerialPort module triggering events in the QT main loop when bytes are received on the serial port. I am not familiar enough with nanovna-saver to make a suggestion or even be sure that this module can be used, but my experience on a simpler project is that QT callbacks are way easyer to maintain than a separate thread blocking on the serial port and locks.

[zarath]

I'm happy that the device code is independent of Qt.. so I prefer to keep it.