Performance and stability improvements on all platforms.

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

Change-Id: Iade1d7897ec5a0f1495c8e157db7ab61dc337e75
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1609647
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.161@{#1}
Cr-Branched-From: 585d822a842f6f9b7d1c16f4537c95ef3491a154-refs/heads/master@{#61438}