Add benchmarking?

[adrn]

It might be good to have benchmarking comparisons for all unxt primitives and overrides against pure-numpy and pure-JAX to check for unexpected overheads in jitted and graded functions that contain units. But after doing some search, it seems like there are no well maintained benchmarking packages for modern Python!

• pytest-benchmark build is failing and not getting recent updates
• asv is currently broken when I tried to use it (same error as reported here) and in general doesn't seem super stable

[nstarman]

I know people use CodSpeed, which has the same API as pytest-benchmark. It looks really good. I've just had some trouble getting it to work with a Jax library on GH's VMs. When I run it locally it works.

[nstarman]

See #265. It's partially working.