RemoveDuplicateVertices Implementation for TriangleMesh (continued)

[shashigk]

Type

• [ ] Bug fix (non-breaking change which fixes an issue): Fixes #
• [x] 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

Checklist:

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

Description

[shashigk]

This is continuation of the PR: https://github.com/isl-org/Open3D/pull/6414