Allocate memory more quickly so the test completes faster. (On the ARM
simulator tests with slow asserts and verify-heap, it was taking around
20 minutes).

Change-Id: I6b4d0a4788817c4f996a073cc3fdf8b69d11bc40
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1973731Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65495}