Windows: Update the hasFrame setting when changing window flags

Since changing the window flags can make it frameless or have a frame
then it should ensure that the hasFrame setting is updated accordingly
when the window flags do.

Change-Id: I7bf4995d7967623b117426d8750e63fa97967e2c
Pick-to: 5.15
Pick-to: 5.12
Fixes: QTBUG-84029
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

src/plugins/platforms/windows/qwindowswindow.cpp

@@ -2152,6 +2152,7 @@ QWindowsWindowData QWindowsWindow::setWindowFlags_sys(Qt::WindowFlags wt,
     QWindowsWindowData result = m_data;
     result.flags = creationData.flags;
     result.embedded = creationData.embedded;
+    result.hasFrame = (creationData.style & (WS_DLGFRAME | WS_THICKFRAME));
     return result;
 }