[benchmark] Use pytest-benchmark for performance regression test

[archibate]

Concisely describe the proposed feature I'd like to make use of the pytest plugin pytest-benchmark instead of our own ad-hoc benchmarking framework which I've done with.

Describe the solution you'd like (if any) First check out the benchmarks/ directory, these are the benchmarks that we've already have. Make function names like benchmark_ -> test_. And make use of that plugin, as describe in their project page. When runing benchmark, simply use pytest benchmarks/. You may change the behavior ti benchmark to follow the same logic as ti test does.

Additional comments

[yuanming-hu]

Thanks for proposing this! pytest-benchmark looks cool, but we certainly need to investigate more before adopting this solution. For example, how well does it support comparison against past results?