Is it possible to access additional vertex properties from ply file?

### 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 have .ply file (which I'm generating) which contains xyz data, normals, color and also one additional property for vertex: confidence (of type uint8).
How can I access this data from C++ code after reading such file using `open3d::io::read_point_cloud()` method? I would like to filter points with highest confidence only.