feat(simu): cross-platform connection of host serial ports to simu radio

[nrw505]

Summary of changes:

• Replaces the old way of connecting simulated radio AUX ports to the host's serial ports.

It's a bit convoluted because QSerialPort has to belong to the main event loop's thread, not the simulator's thread. We rely on QT's signal management to let us shunt data between the threads nicely.