mouse: Move mouse button state from a Uint32 to a formal typedef.

Reference Issue #9812.

include/SDL3/SDL_events.h

@@ -380,7 +380,7 @@ typedef struct SDL_MouseMotionEvent
     Uint64 timestamp;   /**< In nanoseconds, populated using SDL_GetTicksNS() */
     SDL_WindowID windowID; /**< The window with mouse focus, if any */
     SDL_MouseID which;  /**< The mouse instance id, SDL_TOUCH_MOUSEID, or SDL_PEN_MOUSEID */
-    Uint32 state;       /**< The current button state */
+    SDL_MouseButtonFlags state;       /**< The current button state */
     float x;            /**< X coordinate, relative to window */
     float y;            /**< Y coordinate, relative to window */
     float xrel;         /**< The relative motion in the X direction */