Performance and stability improvements on all platforms.

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

Change-Id: I7bba3b26159d9b05ee6129439f9826054f1b44b8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1612702
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.189@{#1}
Cr-Branched-From: 61b56e19f8021e51b99f98d2eba195591548e995-refs/heads/master@{#61513}