MON-109: KeyComposer registers events without needing to add an event listener to it.

- Include the KeyComposer tests in the main test suite. Make them pass. (All were previously failing.)
- Deprecate KeyComposer#addEventListener and ensure events are triggered without calling it.
- Special-case EventManager to look up the event identifier correctly for KeyComposer events, because the identifier should come from the composer, not the target component.

(Tests will not pass until https://github.com/montagejs/montage-testing/pull/9 is merged).