The virtual memory cage supports a fallback mode that attempts to obtain
memory pages within a specific virtual address range by using
PageAllocator hints. However, Prior to this CL, the default
PageAllocator on Fuchsia would ignore hints alltogether, preventing
these mechanisms from working there.

Ultimately, on Fuchsia it would probably be better to manage the virtual
memory cage purely through VMARs instead of actually creating pseudo
mappings just to reserve virtual address space as is currently done
through the PageAllocator. This will require broader changes though, so
in the meantime, sticking to the current PageAllocator API is probably
the best option.

Bug: chromium:1218005
Change-Id: I821cfbb815d81479c3b3310296302addbb9cd8f5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3220340Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Commit-Queue: Samuel Groß <saelo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77398}