This reverts commit 5107ec2a.

Reason for revert: Test is very flaky: https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8%20Linux64

Original change's description:
> Add external backing store JS test
> 
> Allow mocking the limits for ArrayBuffer allocation to simulate operating
> system OOM.
> 
> Bug: chromium:845409
> Change-Id: I38bf56a3677e1db547c774223c81e913f56cb631
> Reviewed-on: https://chromium-review.googlesource.com/1203895
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#55616}

TBR=ulan@chromium.org,mlippautz@chromium.org

Change-Id: I633988dba1b0a87b652e72e0e667e90122e00f6d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:845409
Reviewed-on: https://chromium-review.googlesource.com/1206290Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55630}