idf_monitor: fix gdb issue opening large COM port on Windows
idf_monitor: fix gdb issue opening large COM port on Windows

The GDB uses CreateFile to open COM port on Windows. However this
function requires COM path to be `\\.\COMx` to open COM port whose
number is larger than 10.

Replace the port name from `COM` to `\\.\COM` when on Windows to fix
this.

espressif/esp-idf,espressif/esp-idf,espressif/esp-idf,espressif/esp-idf