@Override
	public GTreeNode next() {
		lastNode = nodeQueue.poll();
		if (lastNode != null) {
			List<GTreeNode> children = lastNode.getChildren();
			nodeQueue.addAll(children);
		}
		return lastNode;
	}
Implements an iterator over all GTreeNodes in some gTree (or subtree).  The nodes are
return in breadth first order.
Ghidra/Framework/Docking/src/main/java/docking/widgets/tree/support/BreadthFirstIterator.java