Performance and stability improvements on all platforms.

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

Change-Id: If74fef3b5b03d856a62c91b27addd54bf03b108a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1605366
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.147@{#1}
Cr-Branched-From: 68449685e96d2774c42bed5988a2a002930c9fa2-refs/heads/master@{#61402}