Flesh out benchmark suite

[rdunnington]

There should be an easy way to examine bytebox performance relative to older versions and other wasm engines under various workloads. The current bench program just prints some simple timings, nothing fancy. Ideally we'd have a one-button command to run a more advanced test suite, complete with visualizations to make it easy to see what areas bytebox perf needs to improve.

This page has some reference implementations of some types of workloads to test: https://benchmarksgame-team.pages.debian.net/benchmarksgame/index.html

[rdunnington]

#81 improves the state of things slightly with a new program json that has larger code size and should be a bit more representative of smaller wasm programs.