Add a new LargeObjectSpace for off-thread allocation. Similar to the
paged OffThreadSpace, it always allocates pages, doesn't participate
in mark or sweep, and can be merged into the OldLargeObjectSpace once
its objects are ready.

Bug: chromium:1011762
Change-Id: I95e2d38b10a9cc5eae4ffd35afef95272e13c731
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1881153
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64727}