Multiple threads can modify async_wraps_ in parallel, which is not ok.

Drive-by-fix:
- Use normal constructor/destructor for AsyncHooksWrap
- Use unique_ptr for storing AsyncHooksWrap

Bug: chromium:1278276
Change-Id: I667980151c775be29e603790e589b1de76fae05a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3338257Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Auto-Submit: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78375}