Implement workers utility

[jasnell]

Provides a utility that can be used to determine if the current thread
is the main Node.js thread or a worker thread, even if worker threads
are not supported.

const { workers } = require('@nearform/node-clinic-common')

console.log(workers.isMainThread)
console.log(workers.threadId)

If workers are not supported on the Node.js version, isMainThread always returns true and threadId always returns 0, otherwise returns the appropriate value.

[goto-bus-stop]

Do we still need the support check, since we're only supporting 10.12+ now?

[jasnell]

I'd actually forgotten that workers had been backported to 10.x :-)

As we spoke about on the phone, if we can make it such that clinic gracefully fails when run on an unsupported version, I think we can avoid adding this utility. Closing this PR with that assumption in mind. Keeping the branch tho in case we need to revisit.

[jasnell]

Actually, it appears this still may be necessary. worker_threads is behind a flag on 10.x (clinicjs/node-clinic-doctor#309 (comment))

[goto-bus-stop]

LGTM in that case 👍

[esmorodin]

Confirm, that fix from clinicjs/node-clinic-doctor/pull/309 works, because otherwise I faced this error: clinicjs/node-clinic#414.
Node version: bash-3.2$ node -v v18.12.0
FYI @jasnell