Have Arrays expose child names

[a10y]

We allow consumers of ArrayData to get the list of all children, we should also make it possible to get the list of child names.

Mostly useful for tools that want to interpret vortex files to have a more useful name then child[0], child[1] etc.

[gatesn]

We sort of do this here, it wouldn't be hard to impl your own visitor to grab child names or we can augment this one

[a10y]

That's recursive though, I just want the immediate children

[a10y]

Like I want the names version of pub fn children(&self) -> Vec<ArrayData>

[joseph-isaacs]

Was working on this as part of something else, see (#1710)