Besides the virtual memory cage, the DecommitPages API is also now
required for Cppgc with crrev/c/3211583.

A working implementation of this API is availabe in src/base/platform
for all supported platforms and is used by the DefaultPlatform.

Bug: chromium:1218005
Change-Id: I29765993ed54bb52de71998ae8c6295637ee4072
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3211584
Commit-Queue: Samuel Groß <saelo@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77396}