ENYO-3928: Expose API for triggering event handler on a control.

Issue
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We need a way to directly trigger a handler for a specific event on a given control.

Fix
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We expose an API method `triggerHandler` that utilizes the `dispatch` method of `Component.`

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>