Performance and stability improvements on all platforms.

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

Change-Id: I5c96407b0e8bdbf2bfc86c4c4db99515a61abf8c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1580910
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.12@{#1}
Cr-Branched-From: d01a6a7788c6f753fd17cf690c18772ad9ad3744-refs/heads/master@{#60961}