Track and publish performance metrics

* We need a benchmark that measures how long it takes to build various targets. This should include minimal "hello world programs", various popular Go libraries, and significant targets in Kubernetes. It should measure clean builds and incremental (single file change) builds.
* This benchmark should be run regularly and automatically (likely in a cron job somewhere).
* The results should be published somewhere that's publically visible (a public Google Sheet with a pretty graph would be a minimum viable product).

No files, tests, or existing entry points are named. First map how Go targets and Kubernetes targets are built, then determine where clean and single-file incremental benchmarks can run on a schedule and how results can be published publicly; done means recurring measurements and visible results for the requested target groups.

Written by the indexing model from the issue text.