How to do out-of-core loading on big pointclouds

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [X] For Python issues, I have tested with the [latest development wheel](https://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](https://www.open3d.org/docs/release/) and the [latest documentation](https://www.open3d.org/docs/latest/) (for `main` branch).

### My Question

I am currently trying to write an Algorithm to create LOD Structures in the form of [3dTiles](https://github.com/CesiumGS/3d-tiles/tree/main/specification).
I load my Pointclouds with open3d, create an octree and use it to form the Tiles while doing some LOD which is not important for this problem.
However doing this is eating my RAM for big clouds so I'm wondering if there is some kind of loading function that can use indices to load specific points from a File or some other kind of out-of-core method to load the Pointcloud.