This reverts commit 13401d2b.

Reason for revert: gc stress breakage

Original change's description:
> [in-place weak refs] Use WeakArrayList in wasm
> 
> Now we can remove FixedArrayOfWeakCells (this was the last user).
> 
> BUG=v8:7308
> 
> Change-Id: I7b74f7833288b20d8f4d098a4afce640ea6db823
> Reviewed-on: https://chromium-review.googlesource.com/1150170
> Commit-Queue: Marja Hölttä <marja@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Reviewed-by: Andreas Haas <ahaas@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#54776}

TBR=marja@chromium.org,mlippautz@chromium.org,ahaas@chromium.org

Change-Id: I1bc1ad7e27813aeaaf191efdf74b865d676475f5
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7308
Reviewed-on: https://chromium-review.googlesource.com/1154787Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54778}