Another encoding fix and test coverage for it.

No-Try: true
Bug: chromium:1292013
Change-Id: Id54f505848f93b4869710156fa77ad2e258c5dd6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3447905Reviewed-by: Liviu Rau <liviurau@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79007}