Rename AST structures to Tree and relocate freeing logic

v0/parser/test_module.c

@@ -4,7 +4,7 @@
 #include <stdlib.h>
 
 static void test_parser_module_name(void) {
-	Module* m = test_get_ast();
+	ModuleTree* m = test_get_ast();
 
 	assert_not_null(m, "expected module to be parsed");
 	assert_str("my_module", m->name, "expected name 'my_module'");