[java] Deprecate AST internal API

[oowekyala]

Deprecates and marks @InternalApi in the Java AST:

• Constructors for nodes
• Abstract classes
• Setters

Also removes trash JJTree comments. Nodes can then inherit a better documentation on their jjtAccept method for example.

@jsotuyod The plan is to make those package-private if possible, otherwise internal API. This is not urgent on the 7.0.0 branch though. The next steps for the java-grammar branch are

• Make the parsing of primary expressions stricter (for now they eg accept foo()()::b())
• Then deal with lambda expressions (they should not be a primary prefix)

[pmd-test]

	1 Message
📖	This changeset introduces 0 new violations, 3 new errors and 0 new configuration errors, removes 0 violations, 3 errors and 0 configuration errors. Full report

Generated by 🚫 Danger

[adangel]

I'll merge this soon. I've added a couple of more deprecations, especially, I also deprecated+internalized the constructors of the (now deprecated) abstract base classes.

This is not urgent on the 7.0.0 branch though

Not necessarily, but the sooner, the better: Ideally, we would only make methods package private in PMD 7, that are already deprecated. I guess, that we will get some merge conflicts, when merging master -> pmd/7.0.x or java-grammar the next time...