We should monitor binary size in the performance dashboard.

Probably this makes the most sense to report as additional metrics on the GoBuild* benchmarks, which means integrating this into Sweet. As a starting point, we can just report total binary size. It would be nice to break it out into at least text and data, but that would mostly serve to help us understand changes in binary size.

We do have a way to indicate that certain metrics have an "exact" distribution, but I'm not sure if that's wired into the dashboard analysis.

@mknyszek @prattmic @dr2chase