Re-evaluate project's eslint rules

[kale-stew]

We have not one but three different ymls with eslint configs. We should re-evaluate these, remove the extras where unnecessary and maybe clean up specific overrides for our test dirs.

1. Root config: here
2. Benchmark test config: here
3. Node/browser test config: here

[ryan-roemer]

The root + test one is a very normal, pretty much expected thing to have. The benchmark one could probably be removed and replaced inline with control comments.