[macOS] Only use Decorations#setImage() in Dock if no app bundle set

Currently, there are three possible sources for the Dock icon on macOS
in the order of precedence:

1) An explicitly set icon via
   -Xdock:icon=/path/to/icon.icns
   which calls
   NSApp setApplicationIconImage

2) An implicitly set icon via
   org.eclipse.swt.widgets.Decorations.setImage(Image)
   org.eclipse.swt.widgets.Decorations.setImages(Image[])
   which in passed down to the Dock also via
   NSApp setApplicationIconImage

3) An implicitly set icon in a Bundled.app distrubution via
   CFBundleIconName / CFBundleIconFile in the Info.plist file

1) and 2) use legacy API NSApp setApplicationIconImage which only
supports a single fixed NSImage, i.e. there is no support for dark/light
mode and or modern look & feel such as Liquid Glass.

Only 3) (app bundle) supports dynamic icons.

The problem is that 2) currently overwrites whatever 3) has set. On top
of that, the Decorations are typically cross-platform, so in fact this
will prevents using a macOS-specific icon at all.

We want to prefer 3) over 2), i.e. only pass down the decorations
whenever we are *not* an app bundle with a declared image.

Similar coding also exists in the JVM, where the dock icon is only set
if we are *not* in an app bundle that specifies an icon:

https://github.com/openjdk/jdk21u/blob/8c322f5953ae161d793213f92d13a1f53d995883/src/java.desktop/macosx/native/libosxapp/NSApplicationAWT.m#L280-L290

Author: sratz

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

@@ -515,7 +515,7 @@ public void setImage (Image image) {
 	if (image != null && image.isDisposed()) error(SWT.ERROR_INVALID_ARGUMENT);
 	this.image = image;
 	if (parent != null) return;
-	if (display.dockImage == null) {
+	if (display.dockImage == null && !display.isBundledIconSet()) {
 		display.application.setApplicationIconImage (image != null ? image.handle : null);
 	}
 }
@@ -552,7 +552,7 @@ public void setImages (Image [] images) {
 	}
 	this.images = images;
 	if (parent != null) return;
-	if (display.dockImage == null) {
+	if (display.dockImage == null && !display.isBundledIconSet()) {
 		if (images != null && images.length > 1) {
 			Image [] bestImages = new Image [images.length];
 			System.arraycopy (images, 0, bestImages, 0, images.length);

bundles/org.eclipse.swt/Eclipse SWT/cocoa/org/eclipse/swt/widgets/Display.java

@@ -3441,6 +3441,17 @@ boolean isBundled () {
 	return false;
 }
 
+boolean isBundledIconSet () {
+	NSBundle mainBundle = NSBundle.mainBundle();
+	if (mainBundle != null) {
+		NSDictionary info = mainBundle.infoDictionary();
+		if (info != null) {
+			return info.objectForKey(NSString.stringWith("CFBundleIconName")) != null || info.objectForKey(NSString.stringWith("CFBundleIconFile")) != null ;
+		}
+	}
+	return false;
+}
+
 static boolean isValidClass (Class<?> clazz) {
 	String name = clazz.getName ();
 	int index = name.lastIndexOf ('.');