Transition to pyproject.toml & update workflows

[ajasmin]

Changes submitted:

• Move project metadata from setup.py to pyproject.toml
• Add the Cython compiler as a build time requirement in pyproject.toml for isolated builds
• Setup setuptools-scm for taking the release version from git tag
• Update GitHub Actions
  • Use a single workflow based on pypa/cibuildwheel example
  • An sdist is now also published on PyPi by the workflow
  • We no longer have to install the Cython compiler explicitly (it's a build dependency in pyproject)
  • Maintainer may want to double check the authentication method for PyPi is still valid. See https://blog.pypi.org/posts/2024-01-01-2fa-enforced/

As an user of this project, my needs are:

• sdist on pypi to let pip build the package for unsupported architecture
• Cpython as a build dependency in pyproject.toml (so pip can automatically pull it)

[youyupei]

Thanks for the input!