This uses a new hardware message with Wine internal WM_WINE_CLIPCURSOR message, to notify the foreground window of ClipCursor calls, or resets. It could possibly have used posted messages, like is done to request the desktop to release the clipping rectangle but I figured that a hardware message could be appropriate and is possibly the preferred mechanism to notify the foreground window.
We use QS_RAWINPUT for convenience here, as to automatically release the hardware message, and because this message is somewhat low-level. It could be anything, and maybe QS_MOUSEMOVE, but we'd have to then manually call accept_hardware_message from win32u.
The desktop posted message is kept, as there's no guarantee that the foreground window will be processing its hardware messages when we need, and/or that the desktop window is foreground.