This introduces a {DebugAbort} machine-level operator as well as the
corresponding {ArchDebugAbort} backend instruction. The goal of this is
to speed up snapshot generation due to cheaper "CSA-asserts".

R=jgruber@chromium.org
BUG=v8:6688

Bug: v8:6688
Change-Id: If45f7da0652d4bb920c51ab7a7c41f9670434bbb
Also-By: jgruber@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/628560Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47568}