Add Dockerfile for JDK 20 on Red Hat UBI 9

[cam-rod]

• Splitting the current Dockerfile into two: <= JDK 19 (on CentOS 7) and >= JDK 20 (on Red Hat UBI 9)
  • Dockerfiles don't really support swappable base images (buildah would work better for that), so the solution here is a multi-stage build, with the first stage validating that the JDK matches the file bounds. The stage isn't necessary, but makes for a decent sanity check.
• Updated the CI action by splitting it into CentOS and UBI jobs. Same as above, there isn't an easy way to filter a matrix of JDK versions without switching off Dockerfiles entirely.

Closes #175.

[jmesnil]

you could make the suffix of the base image (centos7 & ubi9) a dist ARG to continue to use a single Dockerfile with the base image being eclipse-temurin:${jdk}-{dist}

Then in the github action, you only need to associate the jdk versions with the dist (eg using env var):

• 11, 17, 19 -> centos7
• 20 -> ubi9

[jmesnil]

You should have a look at https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstrategymatrixinclude to replace:

strategy:
  matrix:
    jdk-version: [11, 17]

with:

strategy:
  matrix:
    include:
      - jdk-version: 11
        dist: centos7
      - jdk-version: 17
        dist: centos7
      - jdk-version: 20
        dist: ubi9

(I've not tested it)

[cam-rod]

made the suggested changes, let me know what you think

[jmesnil]

@cam-rod thanks