Validate LTS 2025 with Elasticsearch 7 and 8

By running the unit tests against ES 7 and 8, as we do currently in 2023 as a post-release step. See:

• The release pipeline: https://github.com/nuxeo/integration-scripts-priv/blob/2023/Jenkinsfiles/release-nuxeo.groovy#L209
• The ES compatibility pipeline (triggered by the above): https://github.com/nuxeo/nuxeo-lts/blob/v2023.18.11/ci/Jenkinsfiles/build-compat-es.groovy

Let's upgrade the Elasticsearch 7/8 image tag to the latest one available.