This reverts commit 2b9a6d89.

Reason for revert: Fails ubsan:
https://build.chromium.org/p/client.v8/builders/V8%20Linux64%20UBSanVptr/builds/770

Original change's description:
> [snapshot] Add BuiltinDeserializerAllocator
> 
> Encapsulates special reservation / allocation behavior for builtin
> deserialization.
> 
> Bug: v8:6624
> Change-Id: Ic784ed43b607c881b356c6e535c9dbe185e1d4cd
> Reviewed-on: https://chromium-review.googlesource.com/716229
> Commit-Queue: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Yang Guo <yangguo@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#48638}

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

Change-Id: I0c6eceb88efe65526499e124acc4a45ee2904c1c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:6624
Reviewed-on: https://chromium-review.googlesource.com/723141Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48641}