Update work-item references after orchestra moves WorkItem to core

Orchestra issue #3610809 unifies its human-work model: the WorkItem entity, its interface and its manager move from the orchestra_inbox submodule into orchestra core, and the manager service is renamed. A few yoyaku tests reference the old locations and must be updated so the yoyaku_orchestra test suite stays green against orchestra 1.x once #3610809 lands.

What changed in orchestra

• Namespace: Drupal\orchestra_inbox\WorkItemInterface (and WorkItemManagerInterface, Entity\WorkItem) move to Drupal\orchestra.
• Service: orchestra_inbox.manager is renamed to orchestra.work_item_manager.
• The orchestra_work_item entity is now provided by orchestra core, not orchestra_inbox; the entity type id is unchanged.

What to update in yoyaku

• yoyaku_orchestra_example BookingWorkflowE2eTest: point the WorkItemInterface use statement and type hints at Drupal\orchestra, and change get('orchestra_inbox.manager') to get('orchestra.work_item_manager').
• The kernel tests that install the orchestra_work_item schema (BookingWorkflowTest, TransactionDeleteCascadeTest, TransactionSubmissionLocatorTest, TransactionInstanceFieldTest, OrderReviewInteractionTest) keep enabling orchestra_inbox and need no source change; just confirm the entity still installs, since orchestra now provides it.

Tests only; no yoyaku runtime code references the moved classes. Land this after orchestra #3610809 merges.