当字符串里面包含逗号 ","时。默认的解析可能会失败

### Search before asking

- [X] I searched in the [issues](https://github.com/apache/iotdb/issues) and found nothing similar.

### Version

1.3.1

### Describe the bug and provide the minimal reproduce step

当字符串里面包含逗号 ","时。默认的解析失败。

### What did you expect to see?

修改DefaultIoTSerializationSchema 的separator;

### What did you see instead?

package org.apache.iotdb.flink;
public class DefaultIoTSerializationSchema implements IoTSerializationSchema> {
...
private String separator = "^_^";

### Anything else?

_No response_

### Are you willing to submit a PR?

- [X] I'm willing to submit a PR!

Start by locating DefaultIoTSerializationSchema in the IoTDB Flink integration and inspect how its separator is used when parsing strings. Reproduce the failure with a value containing a comma, then verify that the chosen separator allows such values to be parsed successfully.

Written by the indexing model from the issue text.