Fix and improve ISS keypoint

[DNKpp]

Type

• Bug fix (non-breaking change which fixes an issue): Fixes Bug with compute_iss_keypoints (failing randomly) #4847
• 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 #

Motivation and Context

During my usage of the ISS Keypoint functionality I encountered some random crashes, which I tried to find the reason for. I explained it here: #4847 (comment)

Secondly there seems to be a more subtile issue in ComputeModelResolution, as the original code only checks for "more than 0" neighbors, but as the query point itself will always be present, this condition will never fail. I adjusted the condition here to >= 2.

Eventually I applied some std algorithms instead of manually written loops, which makes the intent of the code more obvious.

Checklist:

• I have run python util/check_style.py --apply to apply Open3D code style
  to my code.
  Yes, but it crashes due to some strange errors. But resharper is applying the clang-format file anyways.
• 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

This is the error popup

Those are some of the entries of kp_indices

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This change is 

[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]

@benjaminum Is this PR ready to merge? We can ignore the Ubuntu wheel CI failure for now.

[benjaminum]

yes, please merge