request to have Static function to find the neighboring points for each point in the given point cloud.

### 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

In the latest version 1.4, we have a ["Static function to compute the covariance matrix for each point in the given point cloud, doesn’t change the input"](http://www.open3d.org/docs/release/python_api/open3d.geometry.PointCloud.html#open3d.geometry.PointCloud.estimate_point_covariances). in pointcloud python class.
```static estimate_point_covariances(input, search_param=KDTreeSearchParamKNN with knn = 30)```
Can we also have another python api for "Static function to find the neighboring points for each point in the given point cloud, doesn’t change the input"? in open3d.geometry.KDTreeFlann class

```static estimate_point_pcd_tree_search(input, search_param=KDTreeSearchParamKNN with knn = 30)```
Currently in python, I loop each point in point cloud with function call such as following:
```for i in idxPts:
[k,idx,_] = self.pcd_tree.search_radius_vector_3d(pcd.points[i], radius=radius)
self.neighoursDic[i]=idx
```

Which is quite slow in python.

The reason for that is that some local features such as 1st order moments requires computation from neighbouring point per anchor point.

Many Thanks.

### References

_No response_

### Additional information

_No response_