Update AsyncRequest Utility Types

[jackblanc]

Background

We encountered an error in LLB trying to use the asyncRequestIsFailed utility. The function to identify completed requests works, but the other utils do not. Turns out, the completed util has a return type request is Completed<R>, while the others have boolean. TIL TypeScript supports this return type, not sure what it's called!

Acceptance Criteria

• Other utils are updated to use request is _____ return type
• Tests for this behavior: general, but specifically test that if utilFunc(request) { // can access field }