stream: allow async functions as async stateless transforms

[Renegade334]

Undocumented, but intentional: https://github.com/nodejs/node/blob/2ebf53330ddeddc7e49557de8cddc5e7d8180a30/lib/internal/streams/iter/pull.js#L281-L286

[typescript-bot]

@Renegade334 Thank you for submitting this PR!

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1 package in this PR

• node — on npm, on unpkg (author is owner)

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---

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[typescript-bot]

🔔 @microsoft @jkomyno @r3nya @btoueg @Touffy @mohsen1 @galkin @eps1lon @WilcoBakker @chyzwar @trivikr @yoursunny @qwelias @ExE-Boss @peterblazejewicz @addaleax @victorperin @nodejs @LinusU @wafuwafu13 @mcollina @Semigradsky @anonrig — please review this PR in the next few days. Be sure to explicitly select Approve or Request Changes in the GitHub UI so I know what's going on.