In this test we both search and insert a transition in the main thread,
while the background thread searches.

Bug: v8:7790
Change-Id: Ic899f6c36c9bf9f7f5364ea30eb1c875b7ef6535
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2243211
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68878}