Completion: list events from [Event] metadata for first argument of addEventListener() calls

When completion is triggered here:

```
sprite.addEventListener(
------------------------^
```

The completion engine should recognize that it's an `addEventListener()` call and add items for each of the events defined with `[Event]` metadata in the class (and in all superclasses, of course).

Would also make sense for `removeEventListener()`, `hasEventListener()`, and `willTrigger()`.

Start in the completion engine at the argument position shown for addEventListener() and trace how class metadata and superclass information are available. Extend the event completion behavior to addEventListener(), then assess the same behavior for removeEventListener(), hasEventListener(), and willTrigger(); done means [Event] entries from the class hierarchy are offered.

Written by the indexing model from the issue text.