In the case of bugs creating shared->local edges, this lets us catch
dangling pointers via CHECKs before they happen.

Also removed some redundant checks in the shared struct verifier.
Existing heap verification already checks that all of a Heap's pointers
are contained within it.

Bug: v8:12547
Change-Id: Ic7a007b3b6559e3dfd0286fbf869586023c6f801
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3704911Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81335}