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/+/1538320Reviewed-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}