next_enumeration_index is the next free index available to store a
property. ObjectDescriptor tracks this field while instantiating the
literal and updates the next_enumeration_index when finalizing the
instantiation. When adding new properties (named / computed) we were
updating this value to the current value that is being used instead
of next free index. This cl fixes it.

Bug: chromium:1152231
Change-Id: Ica8c36dcabf035db559e29d4573ecd5e53d6062a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2577463
Commit-Queue: Mythri Alle <mythria@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71709}