rdbms 不支持读取db2 xml

When using DataX to load data from DB2 to Doris, I encounter the following errors:
```bash
{"exception":"Code:[DBUtilErrorCode-12], Description:[不支持的数据库类型. 请注意查看 DataX 已经支持的数据库类型以及数据库版本.]. - 您的配置文件中的列配置信息有误. 因为DataX 不支持数据库读取这种字段类型. 字段名:[DESCRIPTION], 字段名称:[2009], 字段Java类型:[com.ibm.db2.jcc.DB2Xml]. 请尝试使用数据库函数将其转换datax支持的类型 或者不同步该字段 .","record":[{"byteSize":10,"index":0,"rawData":"100-100-01","type":5},{"byteSize":26,"index":1,"rawData":"Snow Shovel, Basic 22 inch","type":5},{"byteSize":4,"index":2,"rawData":"9.99","type":4},{"byteSize":4,"index":3,"rawData":"7.25","type":4},{"byteSize":8,"index":4,"rawData":1100793600000,"type":7},{"byteSize":8,"index":5,"rawData":1103385600000,"type":7}],"type":"reader"}
```

Perhaps we can consider adding support for reading XML types from DB2.

The issue does not name any files or tests. Start by locating DataX's DB2 reader handling for the DB2Xml type and reproduce the reported DESCRIPTION failure when loading DB2 data into Doris. Done means DB2 XML fields are either read successfully or have an explicitly tested, supported conversion path.

Written by the indexing model from the issue text.