Is your feature request related to a problem? Please describe.
To correctly identify the series, we send the SeriesIdentifier (see #419) along with the element value to the element event listeners (over/click)

Describe the solution you'd like
Add and call the listeners with the SeriesIdentifier as the second argument of the callback

Describe alternatives you've considered
n/a

Additional context
We should include the SeriesIdentifier to each external listener/callback that needs to identify a series created within the chart.

Kibana Cross Issues
n/a

Checklist

• this request is checked against already exist requests
• every related Kibana issue is listed under Kibana Cross Issues list
• kibana cross issue tag is associated to the issue if any kibana cross issue is present