Add support for orchestration critical sections

As described [here](https://docs.microsoft.com/en-us/azure/azure-functions/durable/durable-functions-orchestrations#critical-sections), orchestrator functions in C# support critical sections. They need to be supported in JavaScript as well.

Read the linked Azure Durable Functions critical-sections documentation first, then locate the orchestration API surface that would expose this behavior in the TypeScript library. Compare the intended JavaScript behavior with the documented C# support; done when equivalent JavaScript orchestration support is implemented.

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