On 32-bit platforms, we generally don't over-allocate backing stores
for Wasm memories. That leads to quadratic overall complexity of
repeated growth operations by a few pages each though. To fix that,
this patch introduces a small over-allocation factor: when we have
to reallocate to grow a memory, we now grow by at least 1/8th of the
memory's previous size.

Bug: chromium:1294262
Change-Id: I89b5e974c75aac78bece8fcd72fb7a2184345153
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3472496
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79193}