deprecate chest_cutout

BUR #17296 has been approved by @nonamethanks.

deprecate chest_cutout

Seems to be equivalent with cleavage cutout. There's a few "above cleavage" cutouts but having the tag for those being called "chest cutout" is only going to cause us issues. Maybe we can call it above cleavage cutout or something.

+1 for a new tag, there are some characters like Kafka from HSR who have a cutout a tad bit higher on the chest if the artist draws it right (the green part of this image), too high to be called cleavage cutout.

The bulk update request #17296 (forum #243408) has been approved by @nonamethanks.