Use jib-maven-plugin for building (Docker) images

Instead of using `maven-exec-plugin` for calling `docker build ....` one can nowadays rely on [`jib-maven-plugin`](https://github.com/GoogleContainerTools/jib/tree/master/jib-maven-plugin) which builds the docker container just with Java means (and therefore does not require `docker` to be installed and the docker daemon to be running).

Start by locating the Maven configuration that invokes maven-exec-plugin and runs docker build, then compare it with the issue's proposed jib-maven-plugin approach. Done means the project can build its Docker image through Jib without requiring a locally installed Docker daemon; the issue names no tests.

Written by the indexing model from the issue text.