This reverts commit f08547af.

Reason for revert: Causes failures due to virtual address space
exhaustion inside the sandbox.

Original change's description:
> [sandbox] Improve the default ArrayBufferAllocator for the sandbox
>
> Rather than using a page allocator and rounding all allocation request
> sizes up to the next multiple of the OS page size, we now use a
> base::RegionAllocator with a "page size" of 128 as a compromise between
> the number of regions it needs to manage and the amount of wasted memory
> due to allocations being rounded up to a multiple of that page size.
> While this is still not as performant as a "real" allocator, it does
> noticeably improve performance when allocating lots of ArrayBuffers.
>
> Bug: chromium:1340224
> Change-Id: I56d1ab066ba55710864bdad048fb620078b2d8c2
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3913346
> Commit-Queue: Samuel Groß <saelo@chromium.org>
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#83396}

Bug: chromium:1340224
Change-Id: I3e3cc18c0e75cac586b7f014a75df1028bbfa86f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3916637
Commit-Queue: Samuel Groß <saelo@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83417}