This reverts commit b8c821f4.

Reason for revert: compile errors, e.g. https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8%20Linux%20-%20builder/39320

Original change's description:
> Extract JSObject class from objects.cc
> 
> I extracted following class member functions to js-objects.cc
> * JSReceiver
> * JSObject
> * JSBoundFunction
> * JSFunction
> * JSGlobalObject
> * JSDate
> * JSMessageObject
> 
> Declaration of all above class are in js-objects.h.
> 
> I also moved AllocationSite::DigestTransitionFeedback used in JSObject::UpdateAllocationSite
> and ShouldConvertToSlowElements used in JSObject and JSArray
> 
> This patch makes compile time of objects.cc from 17.6s to 14.1s on Z840 Linux.
> And js-objects.cc takes 8.69s for compile.
> 
> Bug: v8:7629
> Change-Id: I989f22363667445dd28d7f8c06c81ff79d6ed45f
> Reviewed-on: https://chromium-review.googlesource.com/c/1447916
> Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Reviewed-by: Marja Hölttä <marja@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#59288}

TBR=marja@chromium.org,mstarzinger@chromium.org,titzer@chromium.org,tikuta@chromium.org

Change-Id: I18a8af8a7970f96b2ec3e56b2b1871b4f080ab01
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7629
Reviewed-on: https://chromium-review.googlesource.com/c/1449635Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59289}