This is a reland of 6afd25ff

Original change's description:
> [builtins] Execute binary-embedded builtin code
>
> This CL creates trampolines into binary-embedded builtins on
> isolate-creation, if --stress-off-heap-code is passed.
>
> Note that this still overwrites existing code objects with the
> off-heap trampoline, and that off-heap builtins still exist both in
> the snapshot and the binary. Addressing these points are the next
> steps.
>
> Drive-by-change: More efficient off-heap code lookups now that the
> off-heap memory area has a contiguous and static layout.
>
> Cq-Include-Trybots: luci.v8.try:v8_linux64_fyi_rel_ng
> Bug: v8:6666
> Change-Id: I7e7ef0aa2cd7b8184ae3a13fa02bdcbb4f2c9f86
> Reviewed-on: https://chromium-review.googlesource.com/947969
> Commit-Queue: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#51809}

TBR=mstarzinger@chromium.org

Bug: v8:6666
Change-Id: I4e0684de90733e5f18f6f0ea4832e327d03dfbf7
Cq-Include-Trybots: luci.v8.try:v8_linux64_fyi_rel_ng
Reviewed-on: https://chromium-review.googlesource.com/955595Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51835}