Change compactify performance comparison visualization

[brookslogan]

The stacked barplot shows the total at the same time as the components, but comparisons between components aren't that easy, and the total's not all that important here since it's not breaking down an extremely common workflow. Change the graphic here to either a grouped barplot or to a grouped box-and-whiskers plot.

[brookslogan]

... Or microbenchmark's built-in violin plots.

[brookslogan]

Or just a table (thanks for the idea here @stevenzhou9930).