Replace setup.py with CMake

[Bonifatius94]

Issue:

• building the project relies on python distutils / setuptools that are not suitable for Python C-extensions
• installing dependencies to build against (like numpy) is supported very poorly -> makes a sdist very painful to deploy
• building is not multi-platform capable, i.e. you cannot build for Windows and Mac, just for Linux
• CMake scikit-build + dockcross build envs offer a solution to automate build processes cross-platform

Suggested Solution:

• set up a CMake script (scikit-build) for automating the cross-platform build process
  see: https://scikit-build.readthedocs.io/en/latest/usage.html#example-of-setup-py-cmakelists-txt-and-pyproject-toml
• also have a look at the dockcross project providing dockerized build envs: https://github.com/dockcross/dockcross
• goals of this transformation:
  • make the build process platform-unspecific (not only Linux, but also Windows and Mac)
  • allow running the unified CMake build process on any dockcross build env
  • simplify GitHub workflows, setup tutorials, etc.