test: abstract utility to use Promise.withResolvers for deferred promises

[davidgamero]

followup for #3052

implement feedback from @cjihrig

clean up repeated deferred testing function

adopt Promise.withResolvers() doc link

// old wrapper
function deferred<T = void>() {
        let resolve!: (value: T | PromiseLike<T>) => void;
        const promise = new Promise<T>((done) => (resolve = done));
        return { promise, resolve };
}

// new wrapper
export function deferred<T = void>() {
    return Promise.withResolvers<T>();
}

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