some teams would like to use `kiln test` from concourse. That concourse
could be shared, like runway // tpe concourse instances. These, even
using authentication, are getting rate limited against dockerhub.

Effectively to run kiln test, we'd first need to preload the images
required to build the test image ( every FROM arg used in the Dockerfile)
avoid the pull ibeing executed implicitly when docker build is run by `kiln test`

To avoid having to actually build an image ( which would either require
to preload the images for the Dockerfile or being able to pull from dockerhub)
we could use this flag to run `docker load -i $IMAGE_PATH` instead of building.

this way, the test image can be `acquired` via docker proxy registries..

why?:

because some CI systems cannot get past the dockerhub rate limitation.
We want to use kiln test for the csb tiles. But we use the tpe / runway
concourse. These instances make it impossible to communicate with dockerhub
because of rate limits ( even with authenticated pulls )

We can make the `kiln test` execution work by pre loading the images that
are used as FROM stages in `internal/test/Dockerfile` into the docker host
we start in the concourse task. Essentially we end up pulling the images from
an accessible repository, then we retag them to match the expected FROM args
and that makes the implicit image build work.

Instead it would be nice to avoid having to run the build stage and make kiln
test consume a provided image instead so it can be run offline.

- replace `"` with `\`` quoted strings
- use closer helper function and move defer up