usb: Make WinUSB integration easier

Move the boilerplate Microsoft descriptors for automatically binding the
WinUSB driver on Windows into M-Stack itself.  Add usb_winusb.[c|h] to
house the descriptors and the descriptor functions.
unit_test: Use the automatic WinUSB support in the unit test

Take the Microsoft descriptors out of usb_descriptors.c, and simply define
AUTOMATIC_WINUSB_SUPPORT in usb_config.h.