When testing the serializer (e.g. via --stress-snapshot), raw external
references (i.e. just raw pointers) can be embedded inside the snapshot.
When those pointers are sandboxed, the corresponding external pointer
tag also needs to be encoded in the snapshot. This CL adds the necessary
logic to support this by introducing new serializer Bytecodes for raw
external references and encoding the raw pointers together with the tag.

Bug: v8:10391
Change-Id: I7b3710c2144e19f7507e3f6db537d250d102ee28
Cq-Include-Trybots: luci.v8.try:v8_linux64_heap_sandbox_dbg_ng,v8_linux_arm64_sim_heap_sandbox_dbg_ng
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3762575Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Samuel Groß <saelo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81723}