Performance and stability improvements on all platforms.

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

Change-Id: I81d542480ad1164036df9629c491ac4fa95cc2eb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1627020
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.263@{#1}
Cr-Branched-From: 7b12e3b94b69b3acab17d1b2e8bbb7d4c4ac89d1-refs/heads/master@{#61767}