Gradle Plugins are re-downloaded every build

[Strohgelaender]

Even though Gradle plugins are part of the build, the plugins are not included in the docker image and need to be re-downloaded every build:

Adding mavenlocal as gradle plugin repository does not solve the issue.

It seems that publishToMavenLocal does not include gradle plugins used in the build. We need to find a different approach.

One possibility could be updating the Gradle Offline Dependencies Plugin, which is no longer maintained since 2019.

Also see this discussion: https://discuss.gradle.org/t/need-a-gradle-task-to-copy-all-dependencies-to-a-local-maven-repo/13397/13