Add integration test for benchmarking

[NullHypothesis]

We currently have no easy-to-use test to measure the requests per second that nitriding can sustain. This is important because we occasionally change the networking code and we ought to make sure that we don't make things slower.

A good place to start would be this directory, which contains a lightweight Web server, Dockerfiles, and a Makefile to run a stress test. Ideally, we would run the stress test for each relevant commit and record the results, allowing us to learn if new commits change things for better or worse.