Performance and stability improvements on all platforms.

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

Change-Id: Id8438902a0677b39121b3a5ee19ceb05215e37a3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1614511
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.198@{#1}
Cr-Branched-From: 30bcdcabe6710f44dbbdd339ecb22592ef99dfed-refs/heads/master@{#61570}