Use pytest-benchmark

[maxrjones]

I don't expect it to be significant, but there is likely some overhead added to get_range and get_ranges due to the match; case in #156. I'm wondering if we should set up pytest-benchmark and codspeed-hq to monitor for performance regressions, to prevent needing to manually test performance?

[kylebarron]

It would be great to have pytest-benchmark here. I'm quite skeptical about benchmarks in CI though. I think the best benchmarks are local/on a dedicated machine.

[maxrjones]

IIRC codspeed runs comparative benchmarks on the same machine rather than testing against cached results, but I don't like relying on GitHub apps that much so I'd definitely support only adding pytest-benchmark for developers to run locally.

[kylebarron]

I guess the way I'd think about codspeed is as a way to tell if something went very wrong between PRs, but for small changes I'd trust local results more