Performance and stability improvements on all platforms.

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

Change-Id: I5d337c18fd754b6e9d81176be83e8db894a80d7f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1619153
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.215@{#1}
Cr-Branched-From: fac30cc62d739bb8565cb4831a2ab6483acffe60-refs/heads/master@{#61640}