Revert of [heap] Introduce parallel compaction algorithm. (patchset #9 id:160001...

Revert of [heap] Introduce parallel compaction algorithm. (patchset #9 id:160001 of https://codereview.chromium.org/1343333002/ )

Reason for revert:
Check failed: https://chromegw.corp.google.com/i/client.v8/builders/V8%20Win64/builds/5535/steps/Check%20%28flakes%29/logs/IndependentWeakHandle

Original issue's description:
> [heap] Introduce parallel compaction algorithm.
>
> - The number of parallel tasks is still 1, i.e., we only compact on the main
>   thread.
> - Remove emergency memory (PagedSpace, and CodeRange)
> - Introduce partial compaction of pages.
> - Logic for multiple tasks is in place.
>
> BUG=chromium:524425
> LOG=N
>
> Committed: https://crrev.com/61ea4f55616d3f7bc2ce049a678f16f7475e03e0
> Cr-Commit-Position: refs/heads/master@{#30787}

TBR=hpayer@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:524425

Review URL: https://codereview.chromium.org/1347873003

Cr-Commit-Position: refs/heads/master@{#30788}