Revise heroism infusion

Reworked heroism from 1.6.0 hasn't been a particularly popular inscription and I'm not a fan of disincentivizing opening fights with it considering one shot and spike damage protection is meant to be a big component of the infusion. This version is more similar to how it was in 1.5, though slightly less powerful.

Made sure to be compatible with current saves, but some stuff is a bit oddly structured to do so.