This reverts commit 1233e7c9.

Reason for revert: There were more test failures, e.g. linux nosnap.

Original change's description:
> Reland "[in-place weak refs] Replace Heap::script_list with a WeakArrayList."
> 
> 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/1148340
> Reviewed-by: Marja Hölttä <marja@chromium.org>
> Commit-Queue: Marja Hölttä <marja@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#54639}

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

Change-Id: I60ebd9784416740c92b32aa92e330755d847b882
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7308
Reviewed-on: https://chromium-review.googlesource.com/1148341Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54642}