Allow changing voxels parameters in place for VoxelGrid or allow batch ```add_voxel``` function.

### 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

Currently, in python, there seems to be no way to change parameters of a voxel in place after the VoxelGrid object has been created. My work around has been to create a new VoxelGrid object and iteratively use ```add_voxel```, which is slow. Could we either set voxel parameters in place or have a batch version of ```add_voxel```?

One way to do it would be to add ```set_voxel_color(idx, color)``` and ```set_voxel_grid_index(idx, grid_index)``` since a voxel only has these two parameters.

### References

_No response_

### Additional information

_No response_