Add pathlib support to IO methods in Python

[evbernardes]

Checklist

• I have searched for similar issues.
• For Python issues, I have tested with the latest development wheel.
• I have checked the release documentation and the latest documentation (for master branch).

Proposed new feature or change

According to my tests with Open3D 0.17 with Python 3.10, this is not yet implemented.

It would be nice if the reading/writing methods in Open3D supported pathlib as inputs, since this is the preferred way of dealing with system paths for many people. This way, instead of having to transform the path to a string:

from pathlib import Path
import open3d as o3d
path = Path('./Data/CAD/example.stl')
mesh = o3d.io.read_triangle_mesh(path.as_posix())

Or equivalently:

mesh = o3d.io.read_triangle_mesh(str(path))

We could just directly enter the Path object:

from pathlib import Path
import open3d as o3d
path = Path('./Data/CAD/example.stl')
mesh = o3d.io.read_triangle_mesh(path)

This is, of course, very minor and would just add a little convenience to the code. But this would also be pretty straightforward to implement, which is why I think it is worth it.

[ssheorey]

Definitely a good convenience feature and we would welcome community PRs for this.

[evbernardes]

@ssheorey I'm glad you agree! Do you think this is possible given the use of pybind?

I have never used pybind so I'm not sure where to even start coding a PR for this, but maybe someone else will :)