Should get the metatracing_vms_experiment benchmarks to work and a codespeed site set up

[timfel]

... then we have a set of benchmarks that we can put on a codespeed page. The benchmarks are here: https://github.com/ltratt/metatracing_vms_experiment

Most of the missing methods I could find I have pushed branches for (except String#slice!, but I've opened a separate issue). In fannkuchredux we get a LocalJumpError, break from proc-closure where we shouldn't get one, and we run into the NotImplementedError in the StringFormatter.