Describe the PR

• moved the classes, moved some of them into internal and removed the annotations
• updated release notes
• fixed compatibility layer for maven-pmd-plugin (pmd-compat6)
  • this was a bit trickier
  • but found a solution thanks to https://www.morling.dev/blog/refining-return-type-java-methods-without-breaking-backwards-compatibility/
  • in some classes, we need to keep the old method around, that returns the old type. Basically, we need to have two
    methods, that return the same thing, but as two different (sub-)types, so that maven-pmd-plugin doesn't need to be
    recompiled.
  • according to the integration tests, maven-pmd-plugin with PMD 7 still works :)

Related issues

• Fixes [core] Consolidate n.s.pmd.lang.rule package #3917

Ready?

• Added unit tests for fixed bug/feature
• Passing all unit tests
• Complete build ./mvnw clean verify passes (checked automatically by github actions)
• Added (in-code) documentation (if needed)