Replace manual image instantiation with createImage() for better scaling

Replaced direct image creation using new
Image(...,descriptor.getImageData()) descriptor.getImageData()) with
descriptor.createImage() in AsynchronousViewer and
TreeModelLabelProvider. This change makes icons now render sharply even
at higher zoom levels (e.g.,225%).

Contributes to vi-eclipse/Eclipse-Platform#199

Author: arunjose696

debug/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/AsynchronousViewer.java

@@ -295,7 +295,7 @@ protected Image getImage(ImageDescriptor descriptor) {
 		}
 		Image image = fImageCache.get(descriptor);
 		if (image == null) {
-			image = new Image(getControl().getDisplay(), descriptor.getImageData());
+			image = descriptor.createImage();
 			fImageCache.put(descriptor, image);
 		}
 		return image;

debug/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/TreeModelLabelProvider.java

@@ -149,7 +149,7 @@ public Image getImage(ImageDescriptor descriptor) {
 		}
 		Image image = fImageCache.get(descriptor);
 		if (image == null) {
-			image = new Image(getDisplay(), descriptor.getImageData());
+			image = descriptor.createImage();
 			fImageCache.put(descriptor, image);
 		}
 		return image;