v0.0.0-1595420718

account for build containers

fixes concourse/concourse#5901

Currently there's some odd behaviour for one-off builds -- they appear as
`<team name>///<build name>/<step name>`, but this will be handled in a later
issue.

While working on this, I noticed some blank entries in the output and realized
these corresponded to image check and image pull containers -- these are for
finding and fetching the `image_resource` on a task. I've written a separate
issue to add accounting for these as well.

There is clearly some conceptual duplication between the
`insertResourceWorkloads` and `insertBuildWorkloads` functions -- I can imagine
adding more such functions for the other container types I mentioned above, so
it's probably worth formalizing this as an interface. Instinctively it feels
a Strategy pattern, and I'd like to have a good name for the way these
strategies get aggregated as well. My other thought was to make multiple
Accountant implementations with some means of composing them -- like a monoid
structure on Accountants. Maybe this would look like a `CompositeAccountant`.

There is also some not-so-pretty duplication between the big test cases, and
despite my best efforts at isolation, they are already reaching a 10-second
running time. I assume most of that time is spent waiting for asynchronous
processes in the setup -- I wonder if there is a good way to profile each test
case.

Signed-off-by: Jamie Klassen <jklassen@vmware.com>