Performance and stability improvements on all platforms.

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

Change-Id: I84afd1e478cf652cfcba6dc71e5a858c2feb9a0c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1601331
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.128@{#1}
Cr-Branched-From: a58a937189fc256ed12ea89ee4338f9f535e63d8-refs/heads/master@{#61338}