Revert of Create libsampler as V8 sampler library. (patchset #24 id:460001 of https://codereview.chromium.org/1922303002/ )

Reason for revert:
V8 Linux64 TSAN failure because ThreadSanitizer indicated data race.

Original issue's description:
> Create libsampler as V8 sampler library.
>
> This patch does five things:
>
> 1. Extracts sampler as libsampler to provide sampling functionality support.
> 2. Makes SampleStack virtual so embedders can override the behaviour of sample collecting.
> 3. Removes sampler.[h|cc].
> 4. Moves sampling thread into log.cc as workaround to keep the --prof functionality.
> 5. Creates SamplerManager to manage the relationship between samplers and threads.
>
> The reason we port hashmap.h is that in debug mode, STL containers are using
> mutexes from a mutex pool, which may lead to deadlock when using asynchronously
> signal handler.
>
> Currently libsampler is used in V8 temporarily.
>
> BUG=v8:4789
> LOG=n
>
> Committed: https://crrev.com/06cc9b7c176a6223971deaa9fbcafe1a05058c7b
> Cr-Commit-Position: refs/heads/master@{#36527}

TBR=jochen@chromium.org,alph@chromium.org,fmeawad@chromium.org,yangguo@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:4789

Review-Url: https://codereview.chromium.org/2000323007
Cr-Commit-Position: refs/heads/master@{#36529}