The current implementation of the Image constructor accepting an
ImageGcDrawer does initialize the image with the given width and height
but extracts them from the image data being initialized with the
ImageGcDrawer. This does not take the current device zoom into account
properly, leading to images unexpectedly being rendered for 100% scaling
while they are supposed to be used at 200% scaling.

With this change, images are properly initialized with the given width
and height and using the according device zoom for the image data
generation, leading to a sharp initialization also on 200% monitors.

Serves as a fix for the MacOS part of issue
https://github.com/eclipse-platform/eclipse.platform.ui/issues/2740