Export uncolored point clouds to XYZ - #2630

import numpy as np
import trimesh

cloud = trimesh.PointCloud(np.random.default_rng(7).random((10, 3)))
# on main: ValueError: all the input arrays must have same number of dimensions
e = cloud.export(file_type="xyz")
assert all(len(line.split()) == 3 for line in e.splitlines())
back = trimesh.load(trimesh.util.wrap_as_stream(e), file_type="xyz")
assert np.allclose(back.vertices, cloud.vertices)