Fix pybind __eq__ methods

[boxanm]

Description

Summary:

Fixed an unknown symbol error when importing libpointmatcher's Python bindings on arm64-based MacOS. Also, fixed failing tests on new boost version.

Changes and type of changes (quick overview):

• When importing pypointmatcher in Python on arm64-based MacOS, I was getting this error:

"ImportError: dlopen(/Volumes/CaseSensitive/libpointmatcher/python/pypointmatcher/pypointmatcher_native.cpython-312-darwin.so, 0x0002): symbol not found in flat namespace '__ZNK14PointMatcherIOIfE10PLYElementeqERKS1_'"

Demangling the symbol error, it complains about this function:

bool PointMatcherIO<float>::PLYElement::operator==(const PointMatcherIO<float>::PLYElement&) const

• Following this discussion, I replaced the direct definitions of the __eq__ method with pybind11::self == pybind11::self and pybind11::self != pybind11::self and overwriting the C++ operator== and operator!= with friend functions.
• I think that the issue did not occur on Ubuntu distros due to different build tools, but I'm not certain. In any case, it solves the problem on MacOS.

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Checklist:

Code related

• [x] I have made corresponding changes to the documentation (i.e.: function, class, script header, README.md)
• [x] I have commented hard-to-understand code
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] All tests pass locally with my changes (Check contributing_instructions.md for local testing procedure using libpointmatcher-build-system)

PR creation related

• [x] My pull request base ref branch is set to the develop branch (the build-system won't be triggered otherwise)
• [x] My pull request branch is up-to-date with the develop branch (the build-system will reject it otherwise)

PR description related

• [x] I have included a quick summary of the changes
• [x] I have indicated the related issue's id with # <issue-id> if changes are of type fix
• [x] I have included a high-level list of changes and their corresponding types (See commit_msg_reference.md for details)

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