[Win32] Avoid faulty setting of image list at OS on Tree.setOrientation

[HeikoKlare]

The Windows Tree implementation only registers an image list at the OS control in case an image is set in the first column of an item of the tree. For images in the other columns, they are added to an SWT image list but since the images are embedded by SWT, no image list is registered at the OS.
The implementation of Tree.updateOrientation() does not consider that for the OS control no image list may have been set even if the SWT control manages an image list. As a consequence, calling Tree.setOrientation() on a Tree whose items do not have any image in the first column leads to all those items receiving a white space where an image might be placed as an empty image list is registered at the OS.

This change adapts the Tree.updateOrientation() implementation to only refresh the OS image list for the control in case one was already set before. In addition to calling Tree.setOrientation() this also affects DPI changes when moving the containing shell to a monitor with a different zoom where the same happens because of a call to Tree.updateOrientation().

Fixes #3075

How to reproduce

Execute this snippet:

	public static void main(String[] args) {
		Display display = new Display();
		Shell shell = new Shell(display);
		shell.setLayout(new FillLayout());

		Tree tree = new Tree(shell, SWT.BORDER | SWT.FULL_SELECTION);
		tree.setLinesVisible(true);
		TreeColumn column1 = new TreeColumn(tree, SWT.NONE);
		column1.setWidth(200);
		TreeColumn column2 = new TreeColumn(tree, SWT.NONE);
		column2.setWidth(200);

		Image image = new Image(display, Snippet392.class.getResourceAsStream("eclipse.svg"));

		TreeItem item = new TreeItem(tree, SWT.None);
		item.setText(0, "Hello");
		item.setText(1, "World");
		item.setImage(1, image);
		new TreeItem(item, SWT.None);

		tree.setOrientation(SWT.LEFT_TO_RIGHT);
		shell.setSize(600, 150);
		shell.open();

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

		display.dispose();
	}

With the current code state it gives:

With this change (and without the call to tree.setOrientation()) it gives:

[github-actions]

Test Results (win32)

   34 files     34 suites   5m 25s ⏱️
4 650 tests 4 577 ✅ 73 💤 0 ❌
1 184 runs  1 160 ✅ 24 💤 0 ❌

Results for commit c012752.

♻️ This comment has been updated with latest results.

[github-actions]

Test Results

  176 files  +   30    176 suites  +30   25m 13s ⏱️ + 2m 26s
4 694 tests +    1  4 672 ✅ +    2   22 💤  -  1  0 ❌ ±0 
6 520 runs  +1 088  6 368 ✅ +1 074  152 💤 +14  0 ❌ ±0 

Results for commit 60ac3a1. ± Comparison against base commit 75beb1e.

♻️ This comment has been updated with latest results.

[fedejeanne]

Looks good and works as expected. I added the snippet too.

See also eclipse-platform/www.eclipse.org-eclipse#501