Initializing a KD-tree from padded 3d data

[hgaiser]

First off: thanks for this implementation!

I would like to initialize a KD-tree from (padded) 3D data. In other words, each point consists of 4 f32 values (X, Y, Z, padding). To create a KD-tree on this data I have to create a new vector of [f32; 3] and copy the values into this new vector. This is quite a waste, ideally I would create the KD-tree out of the padded structure directly.

One option I thought off would be for a new_from_iterator method so that I can throw away the padded field on the fly, as kiddo is ingesting the data. I can submit a PR for this, but figured I would open an issue first to discuss the problem. Perhaps I'm overlooking something.

[sdd]

Hi! A FromIterator implementation would be the best approach here. That would allow users to .collect() into a KdTree, which would be convenient and idiomatic. I'd be very happy to accept a PR for it!