export hessian InputStream & OutputStream for serialization extension

[haiyang1985]

• I have searched the issues of this repository and believe that this is not a duplicate.
• I have checked the FAQ of this repository and believe that this is not a duplicate.

Environment

• Dubbo version: 2.7.3
• Operating System version: macOs
• Java version: JDK 1.8

Steps to reproduce this issue

We are going to serialize direct to Hessian OutputStream for protobuf extension, and read directly from InputStream. The change is going to export the Hessian InputStream & OutputStream for direct write.

private final Hessian2ObjectOutput delegate;

protected ProtobufObjectOutput(OutputStream os) {
  this.delegate = new Hessian2ObjectOutput(os);
}

void writeBytesForPBObject(Object obj, Class clazz) throws IOException {
  try (OutputStream os = delegate.getOutputStream()) {
    if (obj instanceof MessageLite) {
      try {
        ((MessageLite) obj).writeTo(os);
      } catch (IOException e) {
        throw new RuntimeException("Google PB序列化失败，序列化对象的类型为" + obj.getClass().getName(), e);
      }
    }
  }
}