It is no longer necessary to postpone the allocation of backing stores
to avoid triggering GC. As such, the logic around ArrayBuffer
deserialization can be simplified.

Bug: v8:10391, v8:11111
Change-Id: I7410392a6e658cd4be77e2192483c6d412b63412
Cq-Include-Trybots: luci.v8.try:v8_linux64_heap_sandbox_dbg_ng,v8_linux_arm64_sim_heap_sandbox_dbg_ng
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3717982Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Samuel Groß <saelo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81384}