Replaces the copy of the STM32 USB library with a submodule.
Uses v2.6.0 as that was roughly the version that was in the
repo. Temporarily adds #undef for MIN and MAX to get it to
compile. Removes the CDC file from the build as a subsequent
change will replace that with a custom class.

Signed-off-by: Nate Karstens <nate.karstens@gmail.com>

Updates the USB driver to tips. Removes the MIN & MAX #undefs
that were temporarily added in the previous patch.

The most important thing to note regarding compatibility is
that USBD_HandleTypeDef::pUserData is now an array.

Signed-off-by: Nate Karstens <nate.karstens@gmail.com>

Renames VCP (Virtual COM Port) functions to better reflect a Pybricks
custom class and makes functions static.

Signed-off-by: Nate Karstens <nate.karstens@gmail.com>

Removes the USB serial driver. A future change will add
functionality for a custom USB driver to the existing
battery charging driver.

Signed-off-by: Nate Karstens <nate.karstens@gmail.com>

Adds a new Pybricks device class and provides the correct
descriptors so that Windows will use the WinUSB driver.

Signed-off-by: Nate Karstens <nate.karstens@gmail.com>

Adds functions to copy and compare UUIDs in little endian
format. USB is a little endian protocol, so this will be
used to encode and decode UUIDs properly on this medium.

Signed-off-by: Nate Karstens <nate.karstens@gmail.com>

Adds versions and capabilities to the BOS Descriptor by
appending dynamically-generated platform descriptors that
use the same UUIDs that are used with BLE and contain the
following values:

 * Firmware version
 * Software (protocol) version
 * Hub capabilities

Signed-off-by: Nate Karstens <nate.karstens@gmail.com>

Configures the USB device and processes pybricks commands.

Signed-off-by: Nate Karstens <nate.karstens@gmail.com>

This moves the USB VID/PID and strings into pbdrvconfig.h, so that each
hub can set the appropriate values. Additionally, since SPIKE Prime and
Robot Inventor use the same firmware, we have to dynamically set the
PID at runtime based on the hub variant.

This adds new defines for the Pybricks USB device class, subclass and
protocol. The class (0xff) is defined by the USB-IF and is the vendor-
specific class. The subclass and protocol are vendor-specific and come
from the first two bytes of the the Pybricks Bluetooth UUIDs.

This allows us to identify hubs running Pybricks when enumerating USB
devices.