[Win32] Update shell icons on DPI change asynchronously

When changing the zoom of the current monitor, the taskbar icon for an
SWT application is not updated properly but is replaced with a generic
executable icon and will only be replaced with the actual application
after quite some time/interaction (if at all). This seems to be caused
by some caching effects of the Windows explorer.

This change defers the refresh of the icons to be executed after all DPI
change processing has been handled. This results in reliable updates of
the application icon once the DPI change processing has finished.

Author: HeikoKlare

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Decorations.java

@@ -1708,15 +1708,6 @@ LRESULT WM_WINDOWPOSCHANGING (long wParam, long lParam) {
 @Override
 void handleDPIChange(Event event, float scalingFactor) {
 	super.handleDPIChange(event, scalingFactor);
-	Image image = getImage();
-	if (image != null) {
-		setImage(image);
-	}
-
-	Image[] images = getImages();
-	if (images != null && images.length > 0) {
-		setImages(images);
-	}
 
 	Menu menuBar = getMenuBar();
 	if (menuBar != null) {
@@ -1730,5 +1721,21 @@ void handleDPIChange(Event event, float scalingFactor) {
 			}
 		}
 	}
+
+	display.asyncExec(() -> {
+		if (isDisposed()) {
+			return;
+		}
+
+		Image image = getImage();
+		if (image != null) {
+			setImage(image);
+		}
+
+		Image[] images = getImages();
+		if (images != null && images.length > 0) {
+			setImages(images);
+		}
+	});
 }
 }