[QoL] Changes to the mechanic of Eternity Cache

Currently, I want to slam T7 % Health modifier from a Sentinel Armour into a Rouge Unique body armour. This is forbidden. The reason is that it would conflict with the base item type.

HOWEVER, since the modifier is class-agnostic, it makes no sense that I cannot do this.

I suggest that instead of forbidding this, we should allow class-specific affixes, and allow class-agnostic affixes like attributes, health, mana, etc.