Support message level custom_metadata on DictionaryBatch (IPC Message field)

### Describe the enhancement requested

Analogous to https://github.com/apache/arrow-java/issues/1035 but for DictionaryBatch.

The Arrow IPC format supports Message level `custom_metadata`, see https://arrow.apache.org/docs/format/Columnar.html#custom-application-metadata and https://github.com/apache/arrow/blob/main/format/Message.fbs#L154

The DictionaryBatch in this implementation currently has no support for this field.

将 DictionaryBatch 的实现与 Apache Arrow issue 1035 中的类似工作进行比较，并检查 IPC Message.fbs 定义中的消息级 custom_metadata 字段。完成标准是 DictionaryBatch 以与 Arrow IPC 格式一致的方式支持该字段；使用 repository 现有的测试验证其行为。

由索引模型根据 Issue 内容生成。