Performance and stability improvements on all platforms.

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

Change-Id: I6f0ca66d1795eb32ae81ecd4586ac5d9d7d5ff9f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1618003
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.210@{#1}
Cr-Branched-From: 99feae230eaba90222c7be14bcd59dfe63a886d3-refs/heads/master@{#61620}