Full switch to scikit-build-core

[purepani]

This is an in-progress switch to using scikit-build-core for the build system.
As of now, I've just added (untested) bindings in cpp for nanobind. I've done this by switching numerical pointers to ndarray types, and then just calling .data() on those new types to get the underlying pointers to the arrays. I'm sure that this can be simplified in the c code, but this is just meant to be as low effort of a switch as possible.
Next would be to fix the python interface to use these bindings correctly, and to set up scikit-build-core as a build dependency.

[purepani]

Just mentioning that I haven't forgotten about this and will get back to this! I've just been quite busy!

[dkazanc]

Happy New Year @purepani ! It's been a year since and I'm just curios about the state of this (obviously no pressure, everyone is busy). You've done a lot here already, so thanks for that, but how far are we from completing you think? Cheers

[purepani]

This fell off my project list for some reason. Let me take a look at it this weekend