Better information scent about nesting

[LeaVerou]

The current UI around nested charts is not bad in terms of information scent, it's totally on par with any good tree view.
But it can do better.

Currently, until you expand, the only indication of the shape of the children is the number of children. However, both this:

and this:

have 3 children, but vastly different "shapes".

What if we could show this on the bar? Possibly not always if too noisy, but maybe just when the number of children is hovered.

Then, we could go even further and make the animation actually communicate something rather than being mostly decorative, by making the bars unfold down from their places in the parent bar chart!

[SachaG]

I like the idea in theory but I'm not sure if it's worth the added visual complexity? Especially since we already use segmented bars in slightly different contexts, which might get confusing…?

[LeaVerou]

@SachaG Btw this was not a "right now" feature at all (but if you get excited and implement something I won't object 😉)

Re: visual complexity, see:

Possibly not always if too noisy, but maybe just when the number of children is hovered.

Though I think if done well it can be not very noisy. But probably depends on #536 since we can't have the diagonal stripes as well.