`slow-odgi`: better benchmarking

[anshumanmohan]

• [x] Carve out benchmarking from testing, so that they can coexist.
• [ ] Refactor code so that printing happens separately from the computing, then time just the computation.
• [ ] Increase resolution: per-algorithm, per graph-per algorithm.
• [ ] Work with Turnt folks to see if they want to make benchmarking easier.