Add status filter argument to work items CSV export

What does this MR do and why?

Expose status argument in WorkItemsCsvExportInput to enable filtering work items by status during CSV export.

The status argument uses Types::WorkItems::Widgets::StatusFilterInputType, which supports filtering by both status ID and name for flexible work item status filtering.

Notes

• Currently, we don’t support the status field in exported or imported CSV files. This will be addressed in the future via #537379.
• Since the work_items_project_issues_list feature flag, which enabled work items CSV export, was enabled by default in %18.4 (!204139 (merged)) and removed in %18.5 (!205003 (merged)), we'll need to backport this MR to earlier versions to prevent the error reported here.

References

• #582862 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Navigate to a work item list at the project or group level.
2. Filter work items by a specific status, for example 'To do'.
3. Select 'Export as CSV' from the three-dots menu.
4. Before the change, an error was raised, preventing users from exporting work items. After exposing the status argument, the CSV export request succeeds.
5. Navigate to http://127.0.0.1:3000/rails/letter_opener/ and confirm that the CSV file only contains work items filtered by status.

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