Merge: Add missing nodes in the AST

Originally, the AST was very abstract and included only node that useful semantically, thus dropped most keywords and symbols during the AST transformation done by sablecc.

After all these years, I was a very bad idea that cause useless complexity for preople that wanted to program precise error messages or develop tools like nitlight or nitpretty.

So, this PR add back most of these nodes in the AST. Future PR may simplify the code of the tools to deal we a more complete AST thus remove heuristics to retrieve the missing tokens.

Pull-Request: #1320
Reviewed-by: Ait younes Mehdi Adel <overpex@gmail.com>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>