CSA::TryLookupElement must check the upper bound for dictionary-mode
indices.
The "stable map + accessor" branch of FastGetOwnValuesOrEntries must
construct its LookupIterator such that it handles the named/indexed
distinction correctly.

Bug: chromium:1029338,chromium:1029369
Change-Id: I17e74ed24c260c5cfc20c61616e75db7d347f7a5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1943164
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65301}