worker: skip main thread when stdio is inherited
Currently, when the main thread is blocked, the console.log calls from the worker are swallowed.
In https://github.com/nodejs/node/issues/25630, @jasnell and @addaleax seems to think the current behavior is correct, but I have to side with @devsnek on this, I think we can do better. Here's my (naive) attempt at this. There are some broken tests with this PR, but I would like to hear more from @nodejs/workers before spending more time on this, in case there are good reasons to disregard this approach.