Return fire issues

[Coolthulhu]

The monster defense function for return fire has a bunch of things done wrong. It copies a large block of the gun actor instead of using it.

• Doesn't error when gun function is not found (ideally, it would be checked in MonsterGenerator::check_monster_definitions())
• Doesn't initialize the NPC in the same way (stats, skills)
• Won't work for weapons that require UPS
• Is a copypaste instead of proper function reuse

Possible solutions:

• Extract function from gun actor, use it in return fire
• Extract shooter stat block from gun actor to monster, use it in gun actor and return fire

There's also the issue of return fire intentionally not working against throwing, which makes it easy to cheese it. The sound check could be changed to just an extra accuracy penalty if the source can't be heard.