Send LeaveEvent as reaction to WM_POINTERLEAVE to reset hover states

Currently items can get stuck in a hovered state when all fingers are
lifted from a touchscreen. This is because we don't react to the
WM_POINTERLEAVE event from Windows. With this patch we translate a
WM_POINTERLEAVE event to a LeaveEvent to remove the hover state from
QtQuick items.

Fixes: QTBUG-62912
Pick-to: 6.5 6.6
Change-Id: I8a6fb6b7ec77457854a75e20277565d1eb89bab6
Reviewed-by: Wladimir Leuschner <wladimir.leuschner@qt.io>
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

src/plugins/platforms/windows/qwindowspointerhandler.cpp

@@ -441,6 +441,8 @@ bool QWindowsPointerHandler::translateTouchEvent(QWindow *window, HWND hwnd,
             if (id != -1)
                 m_lastTouchPoints.remove(id);
         }
+        // Send LeaveEvent to reset hover when the last finger leaves the touch screen (QTBUG-62912)
+        QWindowSystemInterface::handleEnterLeaveEvent(nullptr, window);
     }
 
     // Only handle down/up/update, ignore others like WM_POINTERENTER, WM_POINTERLEAVE, etc.