[Feature][Sqoop] Sqoop --null-non-string --null-string extension modification, increase lzop compression

[EliuGit]

--null-non-string 会根据情况使用 hive支持的null值 '\N',APP中常量FIELD_NULL_PLACEHOLDER已写死且添加时无条件判断.
org.apache.dolphinscheduler.server.worker.task.sqoop.SqoopConstants 31行
org.apache.dolphinscheduler.server.worker.task.sqoop.generator.targets.HdfsTargetGenerator 78行

hdfs压缩时建议加入lzop

[github-actions]

--null-non-string will use the null value'\N' supported by hive according to the situation. The constant FIELD_NULL_PLACEHOLDER in the APP has been written to death and is unconditionally judged when it is added.
org.apache.dolphinscheduler.server.worker.task.sqoop.SqoopConstants line 31
org.apache.dolphinscheduler.server.worker.task.sqoop.generator.targets.HdfsTargetGenerator line 78

It is recommended to add lzop when compressing hdfs

[github-actions]

Hi:

• Thank you for your feedback, we have received your issue, Please wait patiently for a reply.
• In order for us to understand your request as soon as possible, please provide detailed information、version or pictures.
• If you haven't received a reply for a long time, you can subscribe to the developer's email，Mail subscription steps reference https://dolphinscheduler.apache.org/zh-cn/community/development/subscribe.html ,Then write the issue URL in the email content and send question to dev@dolphinscheduler.apache.org.