lib: make diagnostics_channel async iterable

[Qard]

This is just an idea for a possibly helpful extension to the diagnostics_channel feature in #34895. Not sure how valuable this is, so I've pulled it out to a separate PR where people can 👍 or 👎 if they think it's a worthwhile addition.

Depends on: #34895

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

[nodejs-github-bot]

Review requested:

• @nodejs/http
• @nodejs/net

[Qard]

cc @nodejs/diagnostics Now that diagnostics_channel has landed, I'd like to get a fresh look at this to decide if async iterable support is something we want. No docs currently, but I can write some if people think this is a feature worth having.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/34009/

[mmarchini]

diagnostics_channel is implemented fully synchronously, right? If we add async iterablility to it, we'll be adding asynchronocity to the API, which will cause confusion to users (as the timing from the main API and the async API will be wildly different). Unless I'm misunderstanding it, I'm opposed to adding async iterability to this API (it's not an asynchronous API).

[Qard]

Fair point. I didn't implement it as a requirement, so one could use the regular API when sync guarantees are needed, but then that'd need to be documented well and could be a source of confusion. 😕