Implement QueryOrchestrationStatesSegmentedAsync functionality in DurableTask.Emulator (LocalOrchestrationService)

## 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]