Add Multi-JDK images for testing purposes

I believe it would be a worthwhile addition to the project if a multi-jdk image could be made available. A multi-jdk image is an image containing multiple JDK installations within the same image. The list of JDKs could be limited to the ones currently supported (current LTS + latest version).

This image has little benefit for running services but could help a lot for build/testing/ci workflows. Many projects are considering modernizing their build stack by using a recent version of Java while also maintaining compatibility with older LTS versions. Build tools nowasays provide the ability to specify a different JDK to compile and test code. Although `javac` also provides the `--release` flag, there's no equivalent for testing.

Start by surveying the repository's Dockerfiles and scripts for how existing Eclipse Temurin images are built and which JDK versions are supported. Confirm the current LTS and latest-version targets and how testing or CI images are represented. Done means a documented, buildable multi-JDK image is available for build and test workflows.

Written by the indexing model from the issue text.