Revert of [heap] Tracer: Handle incremental marking scopes (patchset #4 id:100001 of https://codereview.chromium.org/2264033002/ )

Reason for revert:
Unittest fails on win32 debug:
https://build.chromium.org/p/client.v8/builders/V8%20Win32%20-%20debug/builds/4188/steps/Check/logs/GCTracerTest.Incremen..

Original issue's description:
> [heap] Tracer: Handle incremental marking scopes
>
> Before this patch all tracing scopes in incremental marking would be reset
> during a gc tracer start/stop cycle. This patch handles scopes the same way it
> does other incremental marking metrics.
>
> Also:
> - Align finalization metric with regular marking metric.
> - Smaller cleanups
>
> BUG=chromium:639818
> R=jochen@chromium.org
>
> Committed: https://crrev.com/300a8f97472b88ff2f94eb977c36b4bf1bedabf1
> Cr-Commit-Position: refs/heads/master@{#38822}

TBR=jochen@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:639818

Review-Url: https://codereview.chromium.org/2275583002
Cr-Commit-Position: refs/heads/master@{#38827}