Before actually failing to allocate, let the background thread help to
sweep all pages of that space.

As a drive-by also rename allocation functions to make background and
main thread allocation more similar.

Bug: v8:10315
Change-Id: I26d4b622de949d4943e35071cee1df8b3d2889c2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2297383Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68843}