Implement "sync" and "jest-worker" implementations with basic "react" scenario.

[ryan-roemer]

Lots of TODOs I'm going to wrap up in separate work and tickets, but as I'm about on parental leave with my 1yo, I'm just getting it all here to kick us off:

Work

• Implementations:
  • sync: Synchronous code on main event loop
  • jest-worker: Uses jest-worker
• Scenarios
  • react: Render random attributed react components in a tight loop for repeat number of times
• Benchmark: benchmark runner with md results. I've provided a key, but I'm measuring both "time to complete the task" (W time) and "amount of progress in main event loop with 1ms timer" (M loops).

Results

Good news

• Using jest-worker makes overall time less with the main event loop doing more using child_process

Medium news

• The degree of speedup didn't seem linear for number of CPUs for jest-worker. I think we may need more analysis here.

Bad news

• Node12 worker threads don't work yet, with this unfun error:

$ node benchmark/runner/index.js
.ERROR DataCloneError: (a, b) =>
  a.slice(0, 10) === b.slice(0, 10) && a.length === b.length could not be cloned.
    at Worker.postMessage (internal/worker.js:223:23)
    at ExperimentalWorker.send (/Users/rye/scm/fmd/ssr-experiments/node_modules/jest-worker/build/workers/NodeThreadsWorker.js:265:18)
    at WorkerPool.send (/Users/rye/scm/fmd/ssr-experiments/node_modules/jest-worker/build/WorkerPool.js:32:34)
    at Farm._process (/Users/rye/scm/fmd/ssr-experiments/node_modules/jest-worker/build/Farm.js:129:10)
    at Farm._enqueue (/Users/rye/scm/fmd/ssr-experiments/node_modules/jest-worker/build/Farm.js:152:10)
    at Farm._push (/Users/rye/scm/fmd/ssr-experiments/node_modules/jest-worker/build/Farm.js:159:12)
    at /Users/rye/scm/fmd/ssr-experiments/node_modules/jest-worker/build/Farm.js:90:14
    at new Promise (<anonymous>)
    at Farm.doWork (/Users/rye/scm/fmd/ssr-experiments/node_modules/jest-worker/build/Farm.js:56:12)
    at JestWorker._callFunctionWithArgs (/Users/rye/scm/fmd/ssr-experiments/node_modules/jest-worker/build/index.js:162:23)

/cc @kevinmstephens

[ryan-roemer]

Merging. I've got some follow-on work that I'll do in other PRs.

Post-merge review most welcome as well as additional work or PRs in this repo!