Fix the pybind reference bug of get_view_control()

[eamonn-zh]

Type

• Bug fix (non-breaking change which fixes an issue): Fixes Visualizer.get_view_control() gives a copy. #6009
• 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

Resolves the issue reported in #6009 that Visualizer.get_view_control() is expected to return a reference but it actually returns a copy, this problem does not exist in older versions of Open3D.

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

Updated the pybind code and fixed the reference issue.

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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.

[stephendb]

this is a pretty nasty bug, is this repo dead?

[ubt0001]

Any progress on this pull request?

[ssheorey]

Thanks @eamonn-zh for this bug fix and to @Kemo-Huang @identxxy and others for investigating this.

[alessiocancian]

@ssheorey can this be released to pypi?

[PieroV]

Hi, this PR breaks the const correctness on the C++ side.

Have you tried to explicit the lambda return type before removing the const overload?

Something like:

            .def(
                    "get_view_control",
                    [](Visualizer &vis) -> &GetViewControl { return vis.GetViewControl(); },
                    "Function to retrieve the associated ``ViewControl``",
                    py::return_value_policy::reference_internal)

[zhangshuoneu]

The bug refixed of version 1.7.0 hasn't been released to pypi. I also countered this problem