Performance and stability improvements on all platforms.

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

Change-Id: I0564f8ba5d6a8a351f3a3276b86885cb1afaa0fc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1628453
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.270@{#1}
Cr-Branched-From: 64d18ccef86ff182d4577cac5a651046557685dd-refs/heads/master@{#61818}