Expand StatEffect to Include `item_type` and `attribute`

[snayff]

Suggested Feature

StatEffect to handle more that just stats (maybe rename?). There are a variety of values we want to amend and we could either split into separate effects or use 1. As the functionality is really similar suggest consolidating.

Requirements

• extend StatEffect to allow changing:
  • resources (gold, morale etc.)
  • game rules (events per level etc.)
  • attributes (can be healed by self etc.)

Additional Context

None.