Implement AST for 'const' expressions. TODO -- add const expressions to compiler

rust_compiler/libs/compiler/src/test/declaration_literal.rs

@@ -56,6 +56,7 @@ fn variable_declaration_numeric_literal_stack_spillover() -> anyhow::Result<()>
             push 7 #h
             push 8 #i
             push 9 #j
+            sub sp sp 3
             "
         }
     );