[Feature]: Separate chart label control for y and y2

[hughess]

Description

Control labels for y and y2 series separately

What problem would this solve?

Currently if you have y and y2 in a chart, turning labels on turns them on for both. Changing label position also applies to both

How should it work?

yLabels, y2Labels, yLabelPosition, y2LabelPosition

and so on for other props, potentially for setting style of the labels (size, bold, colour, etc)