Ray Intersection in multiview scenes

### 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](http://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](http://www.open3d.org/docs/release/) and the [latest documentation](http://www.open3d.org/docs/latest/) (for `master` branch).

### My Question

Hi I have a point cloud video scene that gets reconstucted from recordings of multiple rgbd cameras.

Camera extrinsics and intrinsics are known.

I want to use the RayCasting class in open3d to check for intersections or closest point of approach in the point cloud.

For eg the work flow would be something like.

Pick point A (x1,y1) in rgbd image 1 and corresponding point B (x2,y2) in rgbd image 2.
I would shoot a raw from the respective cameras at the points and try to find the CPA

Is there any function in the rayCasting class that implements this?