[heap] Move remaining MemoryAllocator functions

Moves several functions missed in
https://chromium-review.googlesource.com/c/v8/v8/+/2203206.

Bug: v8:10473, v8:10506
Change-Id: I882410cefe496054b71db24a65133224dc52f23c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2207144
Commit-Queue: Dan Elphick <delphick@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Auto-Submit: Dan Elphick <delphick@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67870}