The build time flag v8_dict_mode_prototypes is ill-named, because it
does not control whether properties are kept in dictionary mode (this
is done by the v8_dict_property_const_tracking flag), but instead it
controls if SwissNameDictionary or NameDictionary is used as the
property backing store for all dictionary mode objects.

This CL renames the flag and updates its description.

Change-Id: If1337838d1b6d8f089c281a77d9ef7cfd4007220
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2786859Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Santiago Aboy Solanes <solanes@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73706}