- Move generic pieces into MemoryController.
- Keep V8's specific factor computations in HeapController.

Bug: chromium:948807
Change-Id: I1c1fc0516a429b19ce6458f75888b3f9d51824ac
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1617678
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61626}