We should not expose antlr specific API into the PMD's node API (this is addressed by [core,swift] Refactor antlr implementation #2463)

AntlrTokenizer is internal but should be impl, because it is needed to implement a language
based on antlr - at least AntlrTokenizer.getCharStreamFromSourceCode

AntlrBaseRule uses already a different concept than JavaccBasedRules
(where is the visitor or is the rule a visitor?). This indicates missing work on API design
in general.

• Those rules use a visitor instead of being a visitor. Having Javacc rules implement the interface is the bad design, which led to duplication of thousands of lines:

Note that because of [core] Add generic visitor interface in pmd-core #2589, we don't actually need language-specific base rule classes anymore. We could just have an AbstractVisitorRule on the model of the Antlr one (the antlr one doesn't need to exist), with a buildVisitor() method that returns an AstVisitor<RuleContext, ?>.

Open question: How can we extend the Antlr nodes (e.g. adding additional getters/attributes to expose some information for XPath)? The issue is, that they're all generated into the same file...

• Moved to [doc] Verify ANTLR Documentation #2501 as this for now just needs to be documented

How does the impl API look like for Antlr-based languages? -> that leads to the documentation

This task probably depends on PMD 7.0.0 API

This task creates another refactoring task (implementing the proposed API).