Benchmarks & various changes

[mariusandra]

• Add tasks per worker setting
• Fix some test deprecation warnings
• Make the benchmark test print graphs
• Add two more types of benchmarks

Depends on #40

[mariusandra]

Also added:

• Better handling of CLI arguments (directly created from the defaultConfig)
• Renamed piscina.test.ts to worker.test.ts
• Exit server if can't connect to redis
• Add __jestSetTimeout inside VM when testing with jest to simulate requests
• Add a simple option to set the log level in order to have less noisy tests
• Chunk test events into batches of 100 for better async. (Waiting for 100 promises 10 times is better than waiting for 10k promises 1 time)

Can be reviewed!