GetOwnElementFromHeap uses LookupIterator which requires heap
allocation. Therefore, we cannot call it from the background thread
with concurrent access.

Bug: v8:7790, v8:11012
Change-Id: I29733db69a8935c7b7585c776ab1a2d7f1265e95
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2465841
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70488}