samples: subsys: usb: webusb: Fix Win10 detection

This patch refactors the usage of MS OS 2.0 descriptors in the
WebUSB sample. The function subset header was removed since it
is not allowed for non-composite devices.
Also, a new random GUID was added for automatic driver installation.

Signed-off-by: Maximilian Deubel <maximilian.deubel@nordicsemi.no>