Bug 263207 [CommonNavigator] Improve DnD tracing and add DnD test suite
There are no DnD tests for the Common Navigator. Also, the CNF has many test utility classes (basically stolen from JDT), these should be moved into a lower level area, and it looks like org.eclipse.ui.test.harness is a good place. (Perhaps we can get the JDT to use these identical versions as well so there is only one copy that everyone uses). Finally, the DnD tracing needs to be improved to show more information and show it more concisely.
tests/org.eclipse.ui.tests.navigator/src/org/eclipse/ui/tests/navigator/DisplayHelper.java
DisplayWaiter.Timeout timeoutState= waiter.start(timeout);
		boolean condition;
		try {
			do {
				if (display.sleep())
					driveEventQueue(display);
				condition= condition();
			} while (!condition && !timeoutState.hasTimedOut());
		} finally {
			waiter.stop();
		}
		return condition;
	}
	
	/**
	 * Call {@link Display#sleep()} and run the event loop until the given
	 * timeout has elapsed.
	 * <p>
	 * If <code>timeout &lt; 0</code>, nothing happens. If
	 * <code>timeout == 0</code>, the event loop is driven exactly once, but
	 * <code>Display.sleep()</code> is never invoked.
	 * </p>
	 * 
	 * @param display the display to run the event loop of
	 * @param millis the timeout in milliseconds
	 */
	public static void sleep(Display display, long millis) {
		new DisplayHelper() {
			public boolean condition() {
				return false;