Implement octree

[aprokop]

Consider implementing octree, potentially providing a basic container for AMR codes.

[kursatyurt]

Maybe just a note for the future:

A promising algorithm/paper/implementation is Cornerstone

Even though not rigorously tested, I ported a single node versionof it to Kokkos, which performed similarly to the original code.

The algorithm is proven to be scaleable and performs well on GPU too.

[aprokop]

@kursatyurt Thank you for bringing our attention to it. Would you be interested in contributing your implementation to ArborX?

[kursatyurt]

@aprokop Currently, I am struggling with other side projects. As soon as I get a working version of them, I would like to move my tree construction stage to a portable version. It sounds good to directly integrate it into ArboX, as it gets reviewed and improved.

But I don't know when I can have time to bring it here.

[aprokop]

@kursatyurt No worries. Do you have your Kokkos version available somewhere?

[kursatyurt]

@aprokop It is in a private repo. I will clean-up and share it with you.