Determine where historical benchmarking data should live 

As part of https://github.com/coiled/coiled-runtime/issues/148, we'll need to store historical benchmark results somewhere. We should determine where those results should live. For example:

- In this repository
- In a dedicated `coiled-runtime-benchmarks` (or some other name) repository
- In S3
- ...

Related to https://github.com/coiled/coiled-runtime/issues/186