[Fix][Connector-V2][File] Fix Excel write order issues (#10365)

[Wan95u]

Purpose of this pull request

Fixed the issue where Excel output file column order was incorrect. Previously, columns were output in original index order instead of the configured sink_columns order.

Does this PR introduce any user-facing change?

Yes. This fix changes Excel output column order from incorrect (original index order) to correct (sink_columns order). Users who relied on the previous incorrect order will see different output after upgrade.

How was this patch tested?

Added a new test case with reordered columns [3, 1, 2, 0] to verify the fix. All existing tests also pass.

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 necessary, please update incompatible-changes.md to describe the incompatibility caused by this PR.
• 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

[DanielCarter-stack]

Thanks! Two MINOR suggestions:

• ExcelGeneratorTest.java:78 - Test uses sinkColumnsIndexInRow = Arrays.asList(0, 1, 2, 3) with consecutive indices. With consecutive indices, the old code createCell(i) and new code createCell(index++) produce identical results (since i == index). The bug only manifests with non-consecutive indices (e.g., [3, 1, 2, 0]), so the current test cannot verify the fix. Consider adding a test with reordered indices to prevent regression.

• PR Description - The "Does this PR introduce any user-facing change?" section is empty. Since this fix changes Excel output column order from incorrect (original index order) to correct (sink_columns order), users who relied on the previous incorrect order will see different output after upgrade. Documenting this behavior change would help with release notes and user migration.

[corgy-w]

Thank you for your contribution. You should add the corresponding test cases

[Wan95u]

Okay, I will proceed to add test cases in the coming days.

[chl-wxp]

LGTM