Part of #1139

These are the open points from #2417

• Not sure, why sub-packages of a internal package are not excluded -> https://docs.pmd-code.org/apidocs/pmd-core/6.23.0-SNAPSHOT/net/sourceforge/pmd/internal/util/package-summary.html.
  • Should we renamed net.sourceforge.pmd.internal.util into net.sourceforge.pmd.util.internal?
• [lang-test] Upgrade Kotlin, Dokka and Kotest #2870 Not sure, whether the linking to pmd-lang-test really works. Dokka still can't create proper javadoc (see Fail to generate Javadoc with Java 10 (Doclet missing?) Kotlin/dokka#294), but for now, I think, we can't have something better than this: https://docs.pmd-code.org/apidocs/pmd-lang-test/6.23.0-SNAPSHOT/
• Could we also exclude the packages under lang.*.rule.*? IMO the rule implementations should be internal, their Javadoc is irrelevant (from [doc] Generate docs for PMD 7 #1769 (comment))
  • Agreed, that we should be careful with exposing rule implementations. But rather than excluding this package, wouldn't it make sense to move the rule impls into "internal"?
  • Maybe we can do this only for PMD 7...
• Both modules pmd-test and pmd-core have the package net.sourceforge.pmd.lang. That's why the order of the offline links provided to javadoc matters... javadoc only looks at the package list and takes the last offline link, that matches. If the order is swapped, then e.g. the link on https://docs.pmd-code.org/apidocs/pmd-java/6.23.0-SNAPSHOT/net/sourceforge/pmd/lang/java/JavaLanguageHandler.html to AbstractLanguageVersionHandler would point to pmd-test, where the class is not found.
  • For PMD 7, we should clean this up.
• pmd/7.0.x and java-grammar use the same version number and override each other.
  • However, this should not be a problem, since java-grammar and pmd/7.0.x are kept up to date regularly (thanks Clément!).
• I didn't change pmd.github.io yet. We might change the urls for the doc to point to docs.pmd-code.org - although I'm not sure about the implications for googles search index...
  • this needs an update of sitemap_generator.sh