Add benchmarking of API

[matthew-white]

The goal of this issue is to add benchmarking that we can use to assess the performance of the API. The hope is that this benchmarking will be a tool that we can use to evaluate whether a particular code change affects performance (and to what extent). It will let us ask questions like, "does feature X degrade performance?" or "is Y worth doing for performance reasons even though it adds complexity?"

[matthew-white]

@brontolosone, feel free to edit the description above, or add any notes about your overall approach, or link to conversations that have been ongoing elsewhere.

[lognaturel]

Here's possible inspiration from Sentry about how we might surface benchmark info on Github PRs: getsentry/sentry-javascript#18808 (comment)