refactor(ast): 调整AST结构体和枚举类型的声明表示方式

将结构体、联合和枚举类型的字段表示从向量改为声明指针，
允许name和decl字段为null，更新相关初始化函数的断言检查，
使结构更加灵活并支持不完整类型定义。

BREAKING CHANGE: 修改了scc_ast_type结构体中record和enumeration
子类型的字段表示方法，从fields向量改为decl指针。

libs/parser/src/scc_parser.c

@@ -8,6 +8,13 @@ static void dummy_sema_callback(void *context, scc_ast_node_type_t node_type,
     return;
 }
 
+static scc_ast_type_t *dummy_got_type_callback(void *context,
+                                               const char *name) {
+    (void)context;
+    (void)name;
+    return null;
+}
+
 #define ASSIGN_PTR_OR_DEFAULT(assigned_val, value, default)                    \
     assigned_val = value ? value : default
 
@@ -26,12 +33,15 @@ void scc_parser_init(scc_parser_t *parser, scc_lexer_tok_ring_t *tok_ring,
                               callbacks->on_expr, dummy_sema_callback);
         ASSIGN_PTR_OR_DEFAULT(parser->sema_callbacks.on_type,
                               callbacks->on_type, dummy_sema_callback);
+        ASSIGN_PTR_OR_DEFAULT(parser->sema_callbacks.got_type,
+                              callbacks->got_type, dummy_got_type_callback);
         parser->sema_callbacks.context = callbacks->context;
     } else {
         parser->sema_callbacks.on_decl = dummy_sema_callback;
         parser->sema_callbacks.on_stmt = dummy_sema_callback;
         parser->sema_callbacks.on_expr = dummy_sema_callback;
         parser->sema_callbacks.on_type = dummy_sema_callback;
+        parser->sema_callbacks.got_type = dummy_got_type_callback;
         parser->sema_callbacks.context = null;
     }
 }