[Feature Request] Option to customize or disable the "picking sphere" visual in VisualizerWithEditing

### 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).

### Proposed new feature or change

**Is your feature request related to a problem? Please describe.**
I am using `o3d.visualization.VisualizerWithEditing` for a point cloud interaction tool. When I use `Shift + Left Click` to pick a point, Open3D automatically renders a large golden/yellow sphere at the picked location.

This sphere is too large relative to my point cloud details and obstructs the view. I tried to disable it by setting `opt.show_coordinate_frame = False`, but the sphere persists.

**Describe the solution you'd like**
I would like an option to:
1. Completely disable the visual feedback (the golden sphere) during point picking.
2. Or allow customization of the sphere's radius/color via the API.

**Describe alternatives you've considered**
Currently, I have to scale my entire point cloud up (Gulliver Transformation) to make the fixed-size sphere appear relatively smaller, which is not an ideal workflow.

**Additional context**
- **Open3D Version**: 0.19.0
- **OS**: Windows 10
- **Code snippet**:
```python
# Even with show_coordinate_frame=False, the sphere appears on click
vis = o3d.visualization.VisualizerWithEditing()
vis.create_window()
opt = vis.get_render_option()
opt.show_coordinate_frame = False
vis.run()

### References

_No response_

### Additional information

_No response_