Add lastDamageSource to living entities

[Fusezion]

Is your feature request related to a problem?

Supporting lastDamageSource is from my perspective a better implementation to lastDamageCause and provides the same and more information to the users. Especially in cases where a custom damage type might be defined.

Describe the solution you'd like.

I would like a method added onto LivingEntity preferably like #getLastDamageSource matching it along with getLastDamage and getLastDamageCause

Describe alternatives you've considered.

I haven't considered any alternatives to this implementation

Other

While I'm aware that getLastDamageCause returns EntityDamageEvent I find this behavior of it in poor taste, I would rather use a method provided by minecraft than one that I assume is custom made by the server.