benchmark

Delete unused requirements file, simplify nanobind build file (#1635)

The dependencies are contained in the `pyproject.toml` since it was added.

Switches to header and source file globbing instead of manually listing
the files. The selects for different platforms are removed, as a tradeoff,
we take a single- to low double-digit hit in wheel sizes (between 5 percent
zipped and 12% installed on MacOS 13.4).