Introduce consistent way for plugins to publish and track throughput

[yaauie]

The changes we make to plugins affect throughput, and while we make attempts to reason about these changes to avoid pathological performance regressions, no tools are provided for plugins to consistently measure their throughput or to track changes in throughput over time.

It would be helpful if this shared CI library provided a framework for detecting throughput improvements and regressions.

It may be helpful to use evanphx/benchmark-ips (perhaps with kalibera optional dependency, which provides a bootstrap confidence interval).