This is a reland of dd07cbcf

Original change's description:
> PPC/S390: [heap] Clean-up keys of oldspace weakmaps during scavenge
> 
> Port 6604f182
> 
> Original Commit Message:
> 
>      This CL adds handling for cleaning up weakmap (EphemeronHashTable)
>      keys during scavenge, even if the weakmap resides in oldspace.
> 
> Change-Id: Idf8b6115e57b1229864afefe6ffee85acb5e7547
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1538320
> Reviewed-by: Milad Farazmand <miladfar@ca.ibm.com>
> Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
> Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
> Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
> Cr-Commit-Position: refs/heads/master@{#60446}

Change-Id: I8136d873cfc399c84a4daf4de9a1043f016561cb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1546561
Auto-Submit: Milad Farazmand <miladfar@ca.ibm.com>
Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#60560}