Implement QueryOrchestrationStatesSegmentedAsync functionality in DurableTask.Emulator (LocalOrchestrationService) #1332

Problem

Currently, calling QueryOrchestrationStatesSegmentedAsync on client services that use DurableTask.Emulator (LocalOrchestrationService) results in a NullReferenceException, since the emulator does not implement the instance store query APIs. This breaks scenarios where consumers want to test or query orchestration states in-proc (e.g., for integration testing or local feature development) and depend on behavior parity with instance-backed services like AzureTableInstanceStore.

This is only specific to client using DurableTask.ServiceBus backend in production and using DurableTask.Emulator for local runs.

Expected Behavior

• The emulator should provide a (possibly in-memory) implementation of QueryOrchestrationStatesSegmentedAsync that allows query patterns similar to those in AzureTableInstanceStore.
• Querying orchestration state in local scenarios would enable better automated tests and developer workflows without requiring a full Azure Storage/Table backend.

Actual Behavior

• QueryOrchestrationStatesSegmentedAsync is not implemented and instanceStore is null, so attempting to call it results in a crash (NullReferenceException).
• This is confusing when writing code agnostic to target backend.

To Reproduce

• Use any client with LocalOrchestrationService and call QueryOrchestrationStatesSegmentedAsync.
• Observe the crash.

Suggestions

• Implement QueryOrchestrationStatesSegmentedAsync in the emulator so the query will enumerate in-memory orchestration state.
• At a minimum, gracefully throw NotSupportedException with a clear message instead of returning null or failing with NullReferenceException.

References

• [Issue context and analysis: https://github.com/Azure/durabletask]
• [Emulator implementation: LocalOrchestrationService.cs]