Performance and stability improvements on all platforms.

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

Change-Id: I70fbef9b7eab8af304082cbd34b6ceb7ad46db89
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1605358
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.155@{#1}
Cr-Branched-From: bf9e3e4de893999c5664dc0a74fd26ce5def7d22-refs/heads/master@{#61418}