Fix GC#drawImage methods with additional Transformation

[al-noori]

If a transform is applied via the GC, then both drawImage APIs consider now the best fitting handle by requesting it through the width/height of the full image scaled by the scaleFactor (relating destination width/height to source width/height) times the width/height scaling induced by the transformation.

Note that only the second commit is relevant for the PR. The first one references to the changes made in #2913.

To easily see and test, use the following snippet:

package org.eclipse.swt.snippets;

import org.eclipse.swt.graphics.*;
import org.eclipse.swt.widgets.*;

public class Snippet389 {

public static void main (String [] args) {
	Display display = new Display ();
	Shell shell = new Shell(display);
	shell.setText("Snippet 389");
	ImageFileNameProvider fileNameProvider = zoom -> {
		if (zoom == 200) {
			return "src/org/eclipse/swt/snippets/eclipse32.png";
		} else if (zoom == 100) {
			return "src/org/eclipse/swt/snippets/eclipse16.png";
		}
		return null;
	};
	Image image = new Image(display, fileNameProvider);
	shell.addPaintListener(e -> {
		e.gc.drawImage(image, 0, 0, 32, 32);
		e.gc.drawImage(image, 0, 0, 16, 16, 0, 50, 32, 32);
	});

	shell.addPaintListener(e -> {
		e.gc.setTransform(new Transform(display, 2, 0, 0, 2, 0, 0));
		e.gc.drawImage(image, 25, 0, 16, 16);
		e.gc.drawImage(image, 0, 0, 16, 16, 25, 25, 16, 16);
		e.gc.setTransform(null);
	});

	shell.open ();

	while (!shell.isDisposed ()) {
		if (!display.readAndDispatch ()) display.sleep ();
	}
	display.dispose ();
}
}

Below are screenshots of the snippet on a 100% zoom.

Before:

After:

[github-actions]

Test Results (win32)

   34 files  ±0     34 suites  ±0   4m 36s ⏱️ -1s
4 636 tests ±0  4 563 ✅ ±0  73 💤 ±0  0 ❌ ±0 
  170 runs  ±0    167 ✅ ±0   3 💤 ±0  0 ❌ ±0 

Results for commit 1cb3562. ± Comparison against base commit 97a79df.

♻️ This comment has been updated with latest results.

[arunjose696]

Have tested the changes myself and can see it fixes the said issue.

[HeikoKlare]

There is an attempt to fix the issue with wrongly scaled image data being used when a transform is applied for GEF:

• eclipse-gef/gef-classic#925

We should check if that issue is resolved with this PR as well and there is also a snippet in there to may better test these changes.

[HeikoKlare]

I think it would help to add a comment with an explanation of a link to some explaining source why this calculates the right scale values out of the matrix.
It's not that easy to understand as the matrix of course also contains a rotations, so I have to admit I do not easily understand if/why this calculation is the right one.