Connected Component Clustering with Octree

### 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

Hi Community.

I am stuck with the problem of clustering large point clouds into connected segments.
Basically, I want to achieve the results in the [Cluster DBSCAN](https://www.open3d.org/docs/release/tutorial/geometry/pointcloud.html#DBSCAN-clustering) example.
However, my point clouds exceed 10 Mio. Points. and the DBSCAN algorithm becomes really slow in this range.

The famous CloudCompare software achieves [similar Connected Component segmentation](https://www.cloudcompare.org/doc/wiki/index.php/Label_Connected_Components) with the help of Octree, thus can be more performant.

It would be awsom if there was a way to utilize the open3D Octree functionality to segment large point clouds, but I cannot figure out if or how to code my own method.

Has anyone tried this or dealt with this problem?