LocalAllocationBuffer is used on the background thread so it needs
to use CreateFillerObjectAtBackground for creating filler objects.

Bug: v8:10315
Change-Id: Ifc22d87e1e835cfdd65d82fc79b20ee74b2c87b1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2336795Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69224}