Intent-to-prototype: Atomics.waitAsync

[Iain Ireland]

I am prototyping the Atomics.waitAsync proposal. It is currently stage 3 at TC39.

Summary: Atomics.waitAsync is an asynchronous version of Atomics.wait. Instead of blocking the current thread, it returns a promise that will resolve when the waiter is notified. This allows it to be used on the main thread.

Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1467846

Standard: https://tc39.es/proposal-atomics-wait-async

Platform coverage: all

Preference: javascript.options.experimental.atomics_waitAsync

Other browsers: Shipping in Chrome.

web-platform-tests: Tested in test262: https://github.com/tc39/test262/tree/main/test/built-ins/Atomics/waitAsync

- Iain