Issue:

For a few years now, we've been seen the occasional deprecation warning about setup.py. Including:

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Please avoid running ``setup.py`` directly.
Instead, use pypa/build, pypa/installer or other
standards-based tools.

See https://blog.ganssle.io/articles/2021/10/setup-py-deprecated.html for details.
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and

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Ensure that any custom bdist_wheel implementation is a subclass of
setuptools.command.bdist_wheel.bdist_wheel.

By 2025-Oct-15, you need to update your project and remove deprecated calls
or your builds will no longer be supported.

See https://github.com/pypa/wheel/pull/631 for details.
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2025-Oct is on its way, so let's finally do something about it...

Description of changes:

Follow advice from "Is setup.py deprecated?" page at packaging.python.org

tldr; having a setup.py file is not deprecated, but directly invoking python setup.py is deprecated.

• Add pyproject.toml file (the modern way to configure your package)
  • Move data from setup.py -> pyproject.toml wherever possible (can't move dynamic stuff, like build steps for C extension)
  • Move dev dependencies from requirements-dev.txt -> pyproject.toml [project.optional-dependencies]
    • Now you call pip install ".[dev]", instead of pip install -r requirements-dev.txt. The dev dependencies will be installed by the same command that builds and installs our project.
    • This change isn't 100% necessary, but seemed like the modern way to do things. It's one less step to set things up on your machine. However, you can't install dependencies without ALSO building/installing the package (we can roll this back if we end up hating it)
• Use python3 -m build instead of python3 setup.py sdist bdist_wheel (the modern way to build a wheel for distribution)
  • Sadly, build is a non-core package, so might need to be pip installed before using. Fortunately it's been preinstalled on manylinux images since 2021, so our Linux release process will be OK.
  • I updated our MacOS and Windows machines to have build installed for all python versions, so our release process should be OK.
• STOP calling pip install --upgrade setuptools before pip install .
  • Modern pip installs the "build dependencies" declared in pyproject.toml (setuptools & wheel) in a special isolated environment before it builds our project. We declared setuptools>=75.3.1, so we're guaranteed it will get installed, and be a recent version.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.