V8 can fall back to creating a virtual memory cage that does not have
the desired security properties but at least allows V8 to run when
caging is enabled. This API allows the embedder to determine which kind
of cage is being used, for example for metrics collection.

Bug: chromium:1218005
Change-Id: I6988d0a4fce8aeb1361b30fce8c9c2f68f3b92f9
Cq-Include-Trybots: luci.v8.try:v8_linux64_heap_sandbox_dbg_ng
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3220343
Commit-Queue: Samuel Groß <saelo@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77392}