Performance and stability improvements on all platforms.

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

Change-Id: I7d9ebb44f44509df5303ec896e08d26c05a890f0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1595959
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.99@{#1}
Cr-Branched-From: cd59cb86f62f041e03f5b5bd54be828fa82bbf29-refs/heads/master@{#61226}