Support multiple DataLabels

User Story

As a developer, I want to add multiple DataLabels so that a point/series can have multiple data labels.

Acceptance Criteria

describe the final result from the owner's point of view to be counted as completed

Can set multiple DataLabels objects in a point/series.

Details

Put document or specification reference

https://api.highcharts.com/highcharts/plotOptions.series.dataLabels (since 6.2.0)
https://api.highcharts.com/highcharts/series.treemap.data.dataLabels
https://jsfiddle.net/gh/get/library/pure/highcharts/highcharts/tree/master/samples/highcharts/plotoptions/series-datalabels-multiple