Reproduce spec portions order and grouping

[atd]

When using rspec, specs are executed with a given seed that determines spec order. This is useful for reproducing failing specs in CI later in local.

When using flatware, there would be awesome if we had a similar way to reproduce execution order and reproduce errors.

[jdelStrother]

I started looking into this because I wanted something to replace parallel_test's reproduction step -

though it seems a little harder than I'd hoped, due to having to figure out the Flatware::Job that corresponds to a failing Flatware::Checkpoint . @briandunn have you had any better luck?