We are planning on moving String to kNeverSerialized. For this, we are
modifying its methods to bail out if they encounter a NeverSerialized
non-internalized String.

Bug: v8:7790
Change-Id: Ia83c1385e53707ddec374e1730963c29b928a08c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2615420Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71975}