These functions are now unused within V8, as we need tighter control in
mksnapshot for creating embedded.cc.

Embedders should switch to using SnapshotCreator directly.

Bug: v8:6666
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: Id231b3d1fdf50e06c9278f13d095186364264b86
Reviewed-on: https://chromium-review.googlesource.com/1019442Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52692}