[bug]fill_holes: wrong triangle direction

### 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).

### Describe the issue

Using `fill_holes` in `open3d.t.geometry.TriangleMesh` is simple and effective, but the result of filled triangles were create with wrong directions, e.g.:
and cannot be fixed by `compute_vertex_normals`:

is this a bug? can we configure the triangle direction in `fill_holes`?
Or how to flip the directions of the filled holes?

### Steps to reproduce the bug

```python
import open3d as o3d

mesh = o3d.io.read_triangle_mesh('path')
# ....

# try fill holes
filled = o3d.t.geometry.TriangleMesh.from_legacy(mesh)
final = filled.fill_holes()
final.compute_vertex_normals()

o3d.visualization.draw(final)
```

### Error message

_No response_

### Expected behavior

_No response_

### Open3D, Python and System information

```markdown
- Operating system: macOS 10.15
- Python version: Python 3.11.4
- Open3D version: 0.18
- System architecture: apple-silicon
- How did you install Open3D?: pip
```

### Additional information

The similar functions/filter in other software such as MeshLab, MeshFix would fix holes with right normal/direction