This reverts commit dc1af6a2.

Reason for revert: Diff in patchset 2

Original change's description:
> Revert "cppgc: Initial marking loop"
> 
> This reverts commit fb9a19fe.
> 
> Reason for revert: https://ci.chromium.org/p/v8/builders/ci/V8%20Linux64%20UBSan/11028
> 
> Original change's description:
> > cppgc: Initial marking loop
> > 
> > This CL introduces:
> > - Worklist
> > - MarkingHandler to manage gc marking phase
> > - Integration into CollectGarbage for atomic pause GC
> > - MarkingVisitor for main thread marking
> > 
> > Still missing from this CL:
> > - Proper handling for stack scanning
> > - Handling of previously not fully constructed objects
> > 
> > Bug: chromium:1056170
> > Change-Id: I70ac8534dfb898777cf3a06e3119cac8072174fd
> > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2170526
> > Commit-Queue: Omer Katz <omerkatz@chromium.org>
> > Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> > Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#67642}
> 
> TBR=ulan@chromium.org,mlippautz@chromium.org,bikineev@chromium.org,omerkatz@chromium.org
> 
> Change-Id: I666481f44119771be685bf2555aa0dd5eda83a01
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: chromium:1056170
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2187502
> Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
> Commit-Queue: Nico Hartmann <nicohartmann@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#67643}

TBR=ulan@chromium.org,mlippautz@chromium.org,bikineev@chromium.org,omerkatz@chromium.org,nicohartmann@chromium.org

# Not skipping CQ checks because this is a reland.

Bug: chromium:1056170
Change-Id: I54e963e2aeaaf16069bdcdb019c0ac65e28ef6e2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2187733Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67654}