Core/Creatures: renamed exp column to HealthScalingExpansion and implement support for negative expansion level (-1 means current expansion - often used in battlegrounds)

sql/updates/world/4.3.4/2025_06_18_00_world.sql

@@ -0,0 +1,2 @@
+ALTER TABLE `creature_template`
+	CHANGE `exp` `HealthScalingExpansion` INT NOT NULL DEFAULT 0;