[Feature] Add Heroic Strikethrough to NPC Scaling (#3028)

* [Feature] Add Heroic Strikethrough to NPC Scaling

# Notes
- Adds Heroic Strikethrough support to NPC scaling.
- Cleans up `std::stoul` to use `Strings::ToUnsignedInt` since recent changes.
- Sets default values to sane values and removes support for `NULL` values.

* Update 2023_03_04_npc_scale_global_base_heroic_strikethrough.sql

zone/npc_scale_manager.h

@@ -57,6 +57,7 @@ public:
 		int    attack_delay;
 		int    spell_scale;
 		int    heal_scale;
+		int    heroic_strikethrough;
 
 		std::string special_abilities;
 	};