Account for cached WorkflowIdentifier in RenderTester

[steve-the-edwards]

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After adding in caching for the Workflow Ids we may want to add in consideration of this to the RenderTester so that the ids of any children that are not used (since they are passed in via expectWorkflow) don't have their ids cached (or at least do so harmlessly).

Use case, we had a testRender where the Workflow-under-test had child workflows passed in as mocks. These mocks had cachedIdentifier set and accessed even though they shouldn't be used at all by the RenderTester.