Follow-up CL that finishes TNodifying builtins collection gen.

Added a TODO in CSA since I was encountering errors when trying to
return a JSIteratorResult.

Bug: v8:6949, v8:9396
Change-Id: I1e8a9cf8bce54327dd1fad5bd9531058f096469d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1803344
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63766}