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/+/2187502Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Nico Hartmann <nicohartmann@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67643}