During the string reverts a while back
https://chromium-review.googlesource.com/c/v8/v8/+/2633547 I reverted
some tests that were testing the code that was *not* reverted i.e. the
internalization of external strings.

Bug: v8:7790
Change-Id: I84964791cce712d753fd409cc3c641d9fbbb6550
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2699262Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72809}