Fixes the weights of a couple food items.
Replace objective bash_skill() check with a subjective bash_estimate() check.

This fixes #9753 by allowing group bashers to attempt to bash things they can't bash alone.
Add new group bash flag to a bunch of humanoid monsters, mostly zombies.
Extract calculation of group bashing ability to a helper method.
Reimplement pileon code to handle diagonals as well as cardinal directions.
Convert player:: my_mutations and my_traits from vectors to unordered_sets for speed.
Merge branch 'trait-lookup-speedup' of https://github.com/kevingranade/Cataclysm-DDA into bash
Merge branch 'food-weights' of https://github.com/Rivet-the-Zombie/Cataclysm-DDA into bash