This CL adds basic infrastructure for:
- MakeGarbageCollected
- GarbageCollected and related type traits
- Heap (API / internal)
- Basic allocation based on malloc
- CollectGarbage without marking

This allows for allocation and reclamation through an explicit GC
call. No objects are held alive from any source (stack, globals,
refs), yet.

The exact wiring of platform is future work.

Change-Id: I81b7c0ba7b525188f8c0bf9de3b7af35d34322af
Bug: chromium:1056170
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2120538
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66887}