This reverts commit cfccdf88.

Reason for revert: Was a faulty test.

Original change's description:
> Revert "[in-place weak refs] Replace Heap::script_list with a WeakArrayList."
> 
> This reverts commit 06f556d8.
> 
> Reason for revert: gc stress failures
> 
> Original change's description:
> > [in-place weak refs] Replace Heap::script_list with a WeakArrayList.
> > 
> > BUG=v8:7308
> > 
> > Change-Id: Idd527fc2a2f5bde635441a511e424a83558ab969
> > Reviewed-on: https://chromium-review.googlesource.com/1143467
> > Commit-Queue: Marja Hölttä <marja@chromium.org>
> > Reviewed-by: Jakob Gruber <jgruber@chromium.org>
> > Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#54635}
> 
> TBR=ulan@chromium.org,marja@chromium.org,jgruber@chromium.org
> 
> Change-Id: I6908fa42fcf4a8916a1dc49b865526094f950c66
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: v8:7308
> Reviewed-on: https://chromium-review.googlesource.com/1148280
> Reviewed-by: Marja Hölttä <marja@chromium.org>
> Commit-Queue: Marja Hölttä <marja@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#54636}

TBR=ulan@chromium.org,marja@chromium.org,jgruber@chromium.org

Change-Id: I2451ed0237b69bf17bbe13f4929568ebe2abfc67
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7308
Reviewed-on: https://chromium-review.googlesource.com/1148340Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54639}