Support "r" axis for non-intersecting interaction

[luukdv]

Fixes #9826.

[luukdv]

Right now, adding a test in https://github.com/chartjs/Chart.js/blob/master/test/specs/core.interaction.tests.js for something like type: 'polarArea' and Chart.Interaction.modes.nearest(chart, evt, { axis: 'r', intersect: false }) will fail because of NaN values for various props (for example startAngle). Would be great if someone could give some pointers on the right way of setting up that ArcElement from this test, or how to do this differently.

[kurkle]

I think the test you are trying to add is correct and should work. Could you just add it, so I can easily take a look?

[luukdv]

I've pushed the failing WIP test.

[kurkle]

I've pushed the failing WIP test.

getIndexAngle is based on number of labels, the chart has none. Adding labels fixes the elements, but it seems there is some other issue (the test hits 2 arcs).

[luukdv]

Thanks, that was the culprit. I also fixed the other issue (forgot to disable the legend).