events: add addDisposableListener method to EventEmitter

[jasnell]

This adds new use(...) and useOnce(...) methods addDisposableListener method to EventEmitter that returns a disposable object that will unregister the event listeners when disposed, along with two changes that use the new apis to demonstrate how it can be used to simplify some cleanup.

const ee = new EventEmitter();
{
  using ds = new DisposableStack();
  ds.use(ee.addDisposableListener('foo', () => {});
  ds.use(ee.addDisposableListener('bar', () => {});
  if (something) ds.use(ee.addDisposableListener('baz', () => {});
}
// The event listeners will all be removed automatically when ds is disposed.
// We don't need to separately remember to call removeListener/off to cleanup the event listeners