Further modernization of the build backend to reduce `setup.py` usage

Creating an issue to capture the internal discussions.

Currently both cuda.bindings and cuda.core use setuptools as the build backend and have a mixture of pyproject.toml static declarations and setup.py dynamic logics. We have two choices here:

• Keep setuptools but further reduce the amount of code in setup.py:
  • This seems to become possible with recent setuptools, where Cython extensions can now be declared in pyproject.toml.
• Switch to use scikit-build-core:
  • This has the benefit of reusing CUDA discovery mechanism (FindCUDAToolkit) and other nice build system features provided by CMake (see the relevant discussion in #46).
  • The potential downside is to maintain a custom CMakeLists.txt which is arguably a burden for non-C++ (=C & Python) oriented developers. Our Cython extensions are very simple to build.
    • However, this might become necessary once we start integrating some features from cudax::, e.g. #528.

まず、cuda.bindings と cuda.core の現在の pyproject.toml および setup.py の設定を比較し、次に #46 にリンクされている議論を読んでください。最近の setuptools で Cython 拡張を宣言できるのか、それとも scikit-build-core と CMakeLists.txt が必要なのかを、#528 における将来の cudax:: に関する考慮事項も含めて評価してください。プロジェクトが build backend の方向性とその範囲について合意すれば完了です。