Stress configurations cause maps to be GC'ed too early.
We now keep them alive by storing the object in a global variable.

Bug: v8:10892
Change-Id: If03c42612d9907b3b6d0df8bb2de879857a89e0a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2404774Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69862}