Benchmark refactor - argparse CLI

[Erotemic]

@bwoodsend This is a paired down version of #532 that is ready for review / merging. There are two main features added here:

1. Uses the standard library's cpuinfo module to print CPU details when reporting the results of the benchmarks. This will help ensure that users don't compare incomparable data and can serve as a reminder for what benchmarks can be compared against each other. (whoops)

2. Adds an argparse CLI so the user can specify specific modules to disable. I personally don't care about the other json modules that aren't a drop-in replacement for Python's json module. Also the user can specify a --factor as a fraction to speed up the benchmarks for easier hacking.

To add these two features I had to do a little bit of refactoring. I wanted to make it easy to add / remove any new implementation that might come onto the scene, so I registered each benchmark with it's associated library name using a decorator and am passing the list of library names that the user requested to test to the benchmark functions. (I was very tempted to factor out the global variables but I restrained myself).

Speaking of global variables, I made it such that the external libraries aren't imported until the script knows they are needed. I use importlib to implement this as a loop, and then I set those modules as global variables so the rest of the benchmark structure can work without modification.

Lastly, I added a note about what units the benchmarks were in, because I always confuse myself with that.

[codecov-commenter]

Codecov Report

Merging #533 (052add4) into main (b3f8754) will not change coverage.
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[bwoodsend]

Uses the standard library's cpuinfo module to print CPU details when reporting the results of the benchmarks.

> python -VV
Python 3.10.1
> python -c 'import cpuinfo'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'cpuinfo'

Are you sure it's standard lib?

[Erotemic]

I suppose I was mistaken. It looks like cpuinfo is coming from torch. It's not important enough to add a dependency. I'll remove that.

[bwoodsend]

I think a marginally nicer way to eliminate the global LIBRARIES variable would be to have a class which takes libraries as a parameter and stores it as an attribute, then make all the functions that now take a libraries parameter methods of that class instead. But only marginally nicer. Honestly, if I were that allergic to OOP-destroying global variables then I would have abandoned Python altogether in favour pedantically object oriented, but otherwise underwhelming at every turn, Java 🙃 .

[Erotemic]

I was considering a class that stored the parameters as an alternative. But as marginally nice as that is, this script isn't run as part of a larger system, so the globals only bother me on an aesthetic level, they don't have any major down side that I can see.

When I get around to working on #532 go get nice graphs for the benchmarks (and hopefully t-tests to indicate when there is a high probability regression), I'll be rewriting most of this, so I figured I'll just keep the changes here minimal.

[hugovk]

Thanks!

[hugovk]

Oops, this failed on the CI:

https://github.com/ultrajson/ultrajson/runs/6154659419?check_suite_focus=true

Please could you check it?

Let's also add this to run the benchmark on PRs changing the benchmark script or workflow file:

on:
  push:
    branches:
      - main
  pull_request:
    paths:
      - ".github/workflows/benchmark.yml"
      - "tests/benchmark.py"