Hover and tooltip ordering on combined chart

[Roarster]

When using a combined chart in v2.0 the tooltip and hover that is shown in single mode is always the first element found in a dataset that matches the mouse position. This means that if you have a bar and line chart with the bar as the first dataset then the tooltips for the line chart will never appear if they are on top of the bars. This fiddle has an example:

https://jsfiddle.net/qyfLs1w7/1/

In this example it can be fixed by swapping the ordering of the datasets so that the line comes first but I'm not sure this is the best fix. Perhaps the tooltip could be adjusted to show the details of the latest point to be hovered (by time), I think this would ensure that a point contained within another element would be seen as the active when it was hovered with it reverting to the container once the inner point is no longer hovered.

[etimberg]

This was fixed in #3400

Using the new nearest mode