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.

Inizia confrontando le configurazioni attuali di pyproject.toml e setup.py per cuda.bindings e cuda.core, quindi leggi la discussione collegata in #46. Valuta se le versioni recenti di setuptools possono dichiarare le estensioni Cython o se sono necessari scikit-build-core e un CMakeLists.txt, comprese le considerazioni future su cudax:: in #528. Il lavoro è completato quando il progetto concorda una direzione per il backend di build e il relativo ambito.