get_voxel_center_coordinate() to compute also points not in voxelgrid

### 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).

### Proposed new feature or change

The function get_voxel_center_coordinate() is returning center coordinates only if the query point is included in the VoxelGrid. It would be handy to be able to calculate coordinates also for points that are not yet in the VoxelGrid.

### References

http://www.open3d.org/docs/release/python_api/open3d.geometry.VoxelGrid.html#open3d.geometry.VoxelGrid.get_voxel_center_coordinate

### Additional information

_No response_