Update wasm threads proposal tests and fix cmpxchg_u
<rdar://problem/117102231>
Pull request: https://github.com/WebKit/WebKit/pull/19200
Committed 270828@main (b2062fb65324): <https://commits.webkit.org/270828@main> Reviewed commits have been landed. Closing PR #19889 and removing active labels.
*** Bug 265581 has been marked as a duplicate of this bug. ***