Support NPC attacks with ownedItems Choice Sets

[pedrogrullada]

We have a number of effects for which we filter through the player character's owned items, and not their attacks, such as Runic Weapon, Ghostly Weapon, etc. However, this approach leaves us with a gap when it comes to NPCs, who handle their attacks differently.

We could use an attack filter predicated on the character being an NPC, but that feels like a bandaid to something that maybe ownedItems could handle so that such effects don't have to hold bespoke rule elements for PCs and NPCs.