build: relax open3d and numpy version requirements

[yxlao]

Open3D >= 0.19.0 has fixed support for NumPy 2.x (Open3D issue #6840). This PR relaxes the version requirements for Open3D and NumPy. The user is responsible for ensuring the versions are compatible. We also provide a runtime check that will print out a warning message if Open3D and NumPy are not compatible.

Compatibility test

test_init.py:

import numpy as np
import open3d as o3d

print(f"Open3D version: {o3d.__version__}")
print(f"Numpy version: {np.__version__}")

mesh = o3d.geometry.TriangleMesh()
mesh.vertices = o3d.utility.Vector3dVector(np.array([[0, 0, 0], [1, 0, 0], [0, 1, 0]]))
print(f"Number of vertices: {len(mesh.vertices)}")

Results:

# Previous working case
$ python test_init.py                                                                              
Open3D version: 0.18.0                                                                                                                                  
Numpy version: 1.26.0                                                                                                                                   
Number of vertices: 3

# Incompatible case
$ python test_init.py                                                                              
Open3D version: 0.18.0                                                                                                                                  
Numpy version: 2.2.1                                                                                                                                    
[1]    1844774 segmentation fault  python test_init.py 

# New working case
$ python test_init.py  
Open3D version: 0.19.0
Numpy version: 2.2.1
Number of vertices: 3