Performance and stability improvements on all platforms.

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

Change-Id: If4d0464dad1a53a67fb51dab40c39b63cae1129e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1631565
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.294@{#1}
Cr-Branched-From: e7e233fdb91cc9ea99650460e4667df31d59fc57-refs/heads/master@{#61871}