[Fix][connector-hive] Fix the file_name_expression does not take effect in Hive sink.

[Adamyuanyuan]

[Fix][connector-hive] Fix the file_name_expression does not take effect in Hive sink.

Purpose of this pull request

Respect user-provided file_name_expression; only set default when absent. This keeps backward compatibility while allowing customization.

Does this PR introduce any user-facing change?

not need

How was this patch tested?

not need

Check list

• If any new Jar binary package adding in your PR, please add License Notice according
  New License Guide
• If necessary, please update the documentation to describe the new feature. https://github.com/apache/seatunnel/tree/dev/docs
• If you are contributing the connector code, please check that the following files are updated:
  1. Update plugin-mapping.properties and add new connector information in it
  2. Update the pom file of seatunnel-dist
  3. Add ci label in label-scope-conf
  4. Add e2e testcase in seatunnel-e2e
  5. Update connector plugin_config

[Hisoka-X]

Any test case?

[Adamyuanyuan]

Any test case?

Unit tests have been added.

[Hisoka-X]

Please retry the failed ci.

[corgy-w]

@Adamyuanyuan Please retry the failed ci.

[Adamyuanyuan]

done, thanks.