This commit updates the USB Host Library as follows:
- usb_helpers.h
- Removed dependency on USB Host Library API
- Added function to print string descriptors
- usbh
- Fixed bug where an interface/endpoint could be claimed/allocated multiple times
- Removed redundant device ref_count change
- Added unit test for USB Host Library API usage
- This commit adds the API documentation for the USB Host Library.
- Warnings about the beta API are also added.
- usb_host_misc.h renamed to usb_helpers.h