If an enum case has a type annotation, the corresponding enum constant
has this type. This is useful for typing context slots.

Bug: v8:7793
Change-Id: I8b91c3bd3686048f98cce3c034eec4e36f925e5b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2329631
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69165}