test: add codspeed benchmarks

[tlambert03]

this was accidentally committed this to main and then reverted... testing benchmarks on CI with codspeed.io

[codecov-commenter]

Codecov Report

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[tlambert03]

ok, some things learned:

• the runner is much slower than my local computer. benchmarks take forever. So while codspeed.io probably would be good for catching regressions on critical functions run on smaller bits of data, it's probably not a good solution for measuring larger real-world datasets (that's harder of course, and likely scales with performance on smaller problems anyway)
• the last benchmark job (with dramatically reduced data size) did run successfully, but failed on upload: https://github.com/funkelab/motile/actions/runs/4544180511/jobs/8009860945?pr=37 ... so would require @funkey or someone with admin rights to the funkelab organization to accept the request from codspeed that I recently sent.

will probably pursue different strategies (like line profiling which would be more immediately actionable anyway) and let this sit here until further discussion