Performance and stability improvements on all platforms.

TBR=v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com

Change-Id: I90b95a7e2339e9d33ab1b18f8ce8b13b194b8f17
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1582013
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.20@{#1}
Cr-Branched-From: ae6a47bad7363725adb0904c3886547dbcac2024-refs/heads/master@{#60981}