fix(jqLite): allow `triggerHandler()` to accept custom event

In some scenarios you want to be able to specify properties on the event
that is passed to the event handler. JQuery does this by overloading the
first parameter (`eventName`). If it is an object with a `type` property
then we assume that it must be a custom event.

In this case the custom event must provide the `type` property which is
the name of the event to be triggered.  `triggerHandler` will continue to
provide dummy default functions for `preventDefault()`, `isDefaultPrevented()`
and `stopPropagation()` but you may override these with your own versions
in your custom object if you wish.

Closes #8469
you can skip a ton of stuff if we have no events registered for this event type

`if (eventFns) { ....`