Docstring updates for NearestNeighborSearch and compute_metrics

[benjaminum]

Type

• Bug fix (non-breaking change which fixes an issue): Fixes #
• New feature (non-breaking change which adds functionality). Resolves #
• Breaking change (fix or feature that would cause existing functionality to not work as expected) Resolves #

Checklist:

• I have run python util/check_style.py --apply to apply Open3D code style
  to my code.
• This PR changes Open3D behavior or adds new functionality.
  • Both C++ (Doxygen) and Python (Sphinx / Google style) documentation is
    updated accordingly.
  • I have added or updated C++ and / or Python unit tests OR included test
    results (e.g. screenshots or numbers) here.
• I will follow up and update the code if CI fails.
• For fork PRs, I have selected Allow edits from maintainers.

Description

• Adding missing documentation and improving format issues for some docstrings for PointCloud and TriangleMesh
• Fix unknown escape sequence warning in make_docs.py
• Proposal of a template docstring to point out pitfalls and make writing docstrings easier template

The rendered template looks like this

[update-docs]

Thanks for submitting this pull request! The maintainers of this repository would appreciate if you could update the CHANGELOG.md based on your changes.

[ssheorey]

We have some info on writing docs here:

https://www.open3d.org/docs/latest/contribute/contribution_recipes.html#documentation

docs/contribute/contribution_recipes.rst

Can we merge these two?

[benjaminum]

Yes, we can and we should remove the docstring::XDocInject parts in "Case 2". It is over engineered and makes updating the documentation difficult due to the multiple locations in the same file.

[benjaminum]

Done

[ssheorey]

sphinx-tabs and sphinx-copybutton are great!