The waiter queue node of JS Atomics.Mutex is now stored in the shared
external pointer table.

Bug: v8:12547
Change-Id: I2f4ce1c705d5e710b49872942702f60edf6c4043
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3721696Reviewed-by: Shu-yu Guo <syg@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Patrick Thier <pthier@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81380}