feat: publish inbound-agent_debian_jdk25_experimental-jlink image

[lemeurherve]

This change enables the publication of an experimental inbound agent image using jlink, based on a Debian JDK25. (Can be extended to other distributions and experiments if needed), and to be published with only one tag, ex: 3355.v388858a_47b_33-1-debian_jdk25-experimental-jlink-not-prod-ready.

In draft until #1132 is merged (or rejected).

Ref:

• Don't use jlink in newer JDKs images until properly tested #1124 (comment)
• Publish experimental jlink image for newer JDK(s) #1131

Testing done

$ make test

# Check that experimental image is pushed on publication
$ export DOCKERHUB_ORGANISATION=hlemeur
$ export PUBLISH_EXPERIMENTAL=true
$ ./build.sh publish
# Check published tags on Docker Hub
$ curl -s "https://registry.hub.docker.com/v2/repositories/${DOCKERHUB_ORGANISATION}/inbound-agent/tags?page_size=100" \
   | jq -r '.results[].name' | sort | grep experimental
3355.v388858a_47b_33-1-debian_jdk25-experimental-jlink-not-prod-ready

Submitter checklist

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