usb: device_next: new USB Video Class implementation

Introduce a new USB Video Class (UVC) implementation from scratch.
It exposes a native Zephyr Video driver interface, allowing to call the
video_enqueue()/video_dequeue() interface. It will query the attached
video device to learn about the video capabilities, and use this to
configure the USB descriptors. At runtime, this UVC implementation will
send this device all the control requests, which it will send to the
attached video device. The application can poll the format currently
selected by the host, but will not be alerted when the host configures
a new format, as there is no video.h API for it yet.

Signed-off-by: Josuah Demangeon <me@josuah.net>