Add async stream interfaces

[haeseoklee]

Summary

Add Swift Concurrency-friendly interfaces on top of the existing RxSwift-based RIBs APIs.

This change keeps RxSwift as the source of truth and adds additive async/await conveniences for observing lifecycle streams, consuming workflow step outputs, confining async sequences to RIB lifecycle, and binding Swift Tasks to existing RIB lifecycle scopes.

Changes

• Add Observable to async sequence bridges:

  • ObservableType.asAsyncStream(...)
  • ObservableType.asAsyncThrowingStream(...)

• Add async lifecycle stream conveniences:

  • InteractorScope.isActiveSequence
  • RouterScope.lifecycleSequence
  • Working.isStartedSequence
  • LeakDetector.statusSequence

• Add Workflow async APIs:

  • Step.asAsyncSequence(...)
  • Step.onAsyncStep(...)
  • AsyncSequence.fork(_:)

• Add lifecycle-scoped task helpers:

  • Interactor.taskOnDeactivate(...)
  • Interactor.throwingTaskOnDeactivate(...)
  • Worker.taskOnStop(...)
  • Worker.throwingTaskOnStop(...)
  • Workflow.task(...)
  • Workflow.throwingTask(...)

• Add async sequence lifecycle confinement:

  • AsyncSequence.confineTo(_:)
  • Uses swift-async-algorithms combineLatest instead of manually implementing combineLatest behavior
  • Adds AnyAsyncSequence<Element> to preserve element type information without requiring typed AsyncSequence<Element, Failure> availability

• Add swift-async-algorithms as a SwiftPM dependency.

• Add tests covering

Notes

The async APIs are added via extensions so existing protocol conformers and mocks remain source-compatible.

RxSwift remains the internal runtime for lifecycle and workflow behavior. The async interfaces bridge from the existing observable streams and disposable lifecycle hooks rather than replacing them.

Close #6

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