Investigate usage of nanobind

[thorstenhater]

nanobind seems like a simpler, faster alternative to pybind11. Especially for the quite expensive connections_on trampoline and friends this might be interesting to check out.

[LecrisUT]

Would be nice to know the priority of this compared to supporting pybind11 3.0. We hit a build failure in Fedora due to hard-coded version check.

[thorstenhater]

Hi, thanks for the mention. I did some exploration with nb, but hit issues with the numpy handling. Nothing
that presents a hard blocker, but definitely requiring some work.

As for pybind11 3.0, I'd suggest making a separate issue, but it's on our radar and we'll provide a fix in the
coming weeks.