Install with scikit-build

Splitting the buildsystem changes that are unrelated to the compiled backend out of https://gitlab.cern.ch/cp3-cms/bamboo/-/merge_requests/148 .

This should improve a few things: the build seems faster, editable installs should work now (pip -e), which only need a rebuild when modifying a C++ part.

I would recommend doing installing in a clean virtualenv when picking up this change, to avoid any potential conflict between the old and new files.