There is room for improvement/refactoring in jmc/core projects. In detail:

Better handling of Spotless and Checkstyle

• Fix calling spotless/checkstyle directly in submodules by refering to a jmc.config.path variable
• Integrate spotless into build workflow

Cleanup of core/pom.xml:

• URL cleanups
• Plugin version bumps

Test projects don't need to be p2 plugin projects since they only test basic functionality but not in the context of Eclipse/OSGI modules.