This CL handles weakcallbacks for resetting WeakMember smart pointers in parallel.

Tracing data for browsing nytimes.com:
CppGC.AtomicWeak
4.628 ms
CppGC.ConcurrentWeakCallback
0.157 ms

Bug: v8:12796
Change-Id: I1e7aa9d27e22985072a8fc332376ac3bd84a3720
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3692433Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Auto-Submit: Jianxiao Lu <jianxiao.lu@intel.com>
Commit-Queue: Jianxiao Lu <jianxiao.lu@intel.com>
Cr-Commit-Position: refs/heads/main@{#81036}