We need to reserve two pages for young objects and objects on
the evacuation candidate page.

Change-Id: I0c4e8f85971676c0b50dfd947678a33dd1b56084
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2224364Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68110}