[Sandbox] Simulate publishing a company's employee tax statements

Simulate publishing every draft employee tax statement for the company for the current tax season year in sandbox. Sandbox-only: in production this endpoint returns a 404.

The company must be in good standing, and every draft statement for the year must have statement data (call Refresh filings first if needed). At least one draft statement for the year must still be unpublished. Physical mail is not sent. The work runs asynchronously and returns an empty response on success. Poll List employee tax statements or listen for employee_tax_statement.updated webhooks as publishing completes.