Automatize classpath construction

Currently both `jacoco` and `junit` classpaths are manually build.

We should automatize them, possibly by retrieving their jar/class files like `test-runner` does in https://github.com/STAMP-project/test-runner/blob/73b7dd02fb1a019c3e209779c23024179804e81a/src/main/java/eu/stamp_project/testrunner/EntryPoint.java#L748-L754

Start by locating the code that manually builds the jacoco and junit classpaths, then compare its approach with the referenced test-runner EntryPoint.java lines 748-754. Done means both classpaths are constructed automatically by retrieving the required jar or class files instead of maintaining them manually.

Written by the indexing model from the issue text.