Hunter: Move Ammo Damage Bonus to a character Pseudostat

[kayla-glick]

Ammo damage can't be added to any ranged attacks generated outside of the hunter package (e.g. Timeworn Strike) due to it causing an import cycle trying to coerce an agent into a HunterAgent. We already have a pseudostat BonusDamage that we use for bonus weapon damage. We should consider a similar stat for ranged bonus damage like ammo to replace the hunter attribute.