worker: initial implementation

Implement multi-threading support for most of the API.

Thanks to Stephen Belanger for reviewing this change in its
original form, to Olivia Hugger for reviewing the
documentation and some of the tests coming along with it,
and to Alexey Orlenko and Timothy Gu for reviewing other
parts of the tests.

Refs: https://github.com/ayojs/ayo/pull/110
Refs: https://github.com/ayojs/ayo/pull/114
Refs: https://github.com/ayojs/ayo/pull/117

PR-URL: https://github.com/nodejs/node/pull/20876


Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Shingo Inoue <leko.noor@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: John-David Dalton <john.david.dalton@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>