This is a reland of 49e3bfd5
Original change's description:
> [snapshot] Move builtins to dedicated snapshot area
> 
> As a first step towards lazy builtin deserialization, this CL moves
> builtins to their own dedicated area in the snapshot blob, physically
> located after startup data and before context-specific data.
> 
> The startup- and partial serializers now serialize all seen builtins as
> references, i.e. they only encode the relevant builtin id (taking care
> to preserve special behavior around the interpreter trampoline and
> CompileLazy). Builtins are later fully serialized by the
> BuiltinSerializer. The separate blobs are finally glued together by
> CreateSnapshotBlob.
> 
> Deserialization takes the same steps: when we see builtin reference
> bytecodes before builtins have been deserialized, we push to a list of
> deferred builtin references. After builtin deserialization, this list is
> iterated and all builtin references are fixed up.
> 
> Bug: v8:6624
> Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
> Change-Id: Idee42fa9c92bdbe8d5b8c4b8bf3ca9dd39634004
> Reviewed-on: https://chromium-review.googlesource.com/610225
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Reviewed-by: Yang Guo <yangguo@chromium.org>
> Commit-Queue: Jakob Gruber <jgruber@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#47596}

Bug: v8:6624
Change-Id: I8bfac56c482d992987c270bf0fea7acd9e4ca0c7
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Reviewed-on: https://chromium-review.googlesource.com/638271Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47705}