Implement enemy difficulty scaling

[ErikOverflow]

Is your feature request related to a problem? Please describe.
Currently enemies don't scale in difficulty as time goes on/the game progresses. There is an Enemy Scale By Level functionality, but the enemy levels don't go up over time or on level change.

Describe the solution you'd like
This can be done through increasing the Enemies' levels over time, having difficulty scale by clearing stages and reaching the next level, a mixture of the 2, or another alternative.

Additional context
This is a very abstract implementation. I would suggest modifying the EnemyScaleByLevel to customize the scaling. You will likely need to create a new script that sets CharacterLevel.