add option to use local test image tarball instead of building the image

[notrepo05]

Please see the original PR authored by nouseforaname: https://github.com/pivotal-cf/kiln/pull/494. Recreating for github action permissions

Copied for convenience:

Long story short, we'd like to run kiln test in a shared concourse.

We are prevented from doing so because we cannot pull the images that https://github.com/pivotal-cf/kiln/blob/main/internal/test/Dockerfile requires for the FROM steps.

We are using authenticated pulls but we still get rate limited.

We'd like to be able to prebuild the required image via the build-oci task and then be able to consume the prebuild image in out kiln test task

../kiln/kiln test --manifest --image-path image.tar.gz
kiln test: 2024/06/06 10:43:20 connecting to ssh socket "/run/user/1000/keyring/ssh"
kiln test: 2024/06/06 10:43:20 ensuring ssh agent keys are configured
kiln test: 2024/06/06 10:43:20 pinging docker daemon
kiln test: 2024/06/06 10:43:20 completed session setup
kiln test: 2024/06/06 10:43:20 loading test image
kiln test: 2024/06/06 10:43:21 loaded image image.tar.gz:
{"stream":"Loaded image: kiln_test_dependencies:vmware\n"}

kiln test: 2024/06/06 10:43:21 creating test container
kiln test: 2024/06/06 10:43:21 created test container with id bc702b3be2c69ee63c9ff035c97e1123c1781ffcc64e819bea09583d5e279e6c
go: downloading github.com/onsi/gomega v1.33.1
go: downloading github.com/pivotal-cf/kiln v0.94.0
go: downloading github.com/onsi/ginkgo/v2 v2.17.2
go: downloading github.com/google/go-cmp v0.6.0
go: downloading gopkg.in/yaml.v3 v3.0.1
go: downloading golang.org/x/net v0.24.0

• add flag to provide docker test image as tarball
• add alternative to execute image-build every time
• implement changes requested on review