[Other] Migrate away from `antlr4ts` to direct Antlr4 TypeScript target generation

[Luna-Klatzer]

Is there an existing issue for this?

• [X] I have searched the existing issues

Current State & Issue

As described in https://github.com/tunnelvisionlabs/antlr4ts/issues/549, the need of using antlr4ts to generate the language Lexer and Parser has vanished, as the base Antlr4 package now provides such functionality as well.

As such to avoid depending on a deprecated project which itself is also incompatible with newer versions, we will need to migrate away and adjust our lexer & parser generation workflows.