This reverts commit f1b1ec70.

Reason for revert: Tentative revert for https://logs.chromium.org/v/?s=chromium%2Fbb%2Fclient.v8.fyi%2FV8-Blink_Mac%2F13696%2F%2B%2Frecipes%2Fsteps%2Fwebkit_unit_tests%2F0%2Fstdout

Original change's description:
> [builtins] Remove off-heap builtins from the snapshot
> 
> This CL is the final major step towards shipping off-heap-safe builtins
> embedded into the binary.
> 
> Prior to snapshot serialization, we now:
> * create the embedded blob containing off-heap instruction streams,
> * use that to generate embedded.cc (containing embedded binary data),
> * replace off-heap-safe builtins with trampolines,
> * and serialize those into the final snapshot.
> 
> The new RelocInfo::OFF_HEAP_TARGET kind is used to fix up trampoline
> targets on deserialization.
> 
> Bug: v8:6666
> Change-Id: Ib07aea9e3bd7ecdec42291c1388b3a7453ea96ce
> Reviewed-on: https://chromium-review.googlesource.com/950775
> Commit-Queue: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Reviewed-by: Yang Guo <yangguo@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#51960}

TBR=yangguo@chromium.org,mstarzinger@chromium.org,jgruber@chromium.org

Change-Id: I58dd4bf9a99d37416855b48807150e1dd9ecd9e8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:6666
Reviewed-on: https://chromium-review.googlesource.com/964363Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51962}