read the serial port from `LAST_config/config/inst.DavisWeather/inst.DavisWeather.create.yml`

[EastEriq]

I strongly suggest to use the same pattern I used for https://github.com/EastEriq/LAST_EnvironmentArduinoSensors:

• make this class inherit from obs.LAST_Handle
• include a .loadConfig() in its creator, like in https://github.com/EastEriq/LAST_EnvironmentArduinoSensors/blob/8da023d7cba81bb97c1f0d9cb465b62fb50c0794/%2Binst/%40serialArduinoSensors/serialArduinoSensors.m#L22
• change the .connect method so that is capable of translating a physical USB port address (which is invariable) into a logical serial port address (which is assigned by the system at every reboot/depends on the order the cables are plugged in). My standard way is like https://github.com/EastEriq/LAST_EnvironmentArduinoSensors/blob/8da023d7cba81bb97c1f0d9cb465b62fb50c0794/%2Binst/%40serialArduinoSensors/connect.m#L25. The functions isPCIusb() and idpath_to_port() come from https://github.com/EastEriq/LAST_USBserial