lang: replace stack-based parser with a recursive parser

lang/ast/discard.c

@@ -1,9 +1,7 @@
-#include "ctx.h"
 #include "node.h"
 
 #include <stdio.h>
 
 struct ast_node_type discard_node_ops = {
-	.n_state_size = sizeof(struct parser_state),
 	.n_node_size = sizeof(struct ivy_ast_discard_node),
 };