Suggestion: use "antlr4.generation.language" for internal code generation

[eternalphane]

It's possible that some rule names may conflict with generated code in target language, e.g. operator in C++, while they are valid identifier names in Java.

[mike-lischke]

The problem with that approach is that the Typescript target cannot produce the required interpreter data, hence it cannot be used for internal parser generation. We could do a fallback to any other language if Typescript is specified, but then we might be back to the original problem.

Now we could introduce another setting, just for internal generation, but that seems pretty odd, since this is something internal and hence per se not configurable by the user.