Update docker build scripts to provide more information to downstream scripts

Looking for an interim approach while designing a bigger refinement to how we do releases at the AdoptOpenJDK project (potentially trigger/choreograph all activities from a central pipeline or workflow), but in the near term, here is what I would like to accomplish:

- at the end of a successful creation of docker images and manifest file I would like to launch testing on all of the images that were produced

- first cut was to trigger testing from the successful finish of the [docker manifest job](https://ci.adoptopenjdk.net/view/Docker%20Images/job/openjdk_build_docker_manifest/) - I have done this in a naive way, but it is problematic. There is no information about JDK_IMPL, JDK_VERSION of what is being run as part of the manifest job (one would have to inspect the console output at present, which is not optimal for an automated approach).

I have currently made the assumption its always running jdk14 and so launch , since the last many runs were for that JDK_VERSION.

What artifacts or information is available from the docker build scripts that can be used to determine what testing to run?