Draft: AST-1102 Use Nanobind instead of Pybind11
This MR is the result of investigating using Nanobind instead of Pybind11. It should not be merged yet (December 2022), since the conclusion is that we should stick with the more stable Pybind11 for now.
Reviewers should thus focus on remaining questions about Nanobind instead of on merging this MR.