Scripts/Events: Globally fix all ExecuteEvent loops to check UNIT_STATE_CASTING after each iteration, instead of just checking it once initially.

Fixes and closes #17892.

(cherry picked from commit ac62d7156f93bf86f57dbad1f24f14031322fd5a)

Drycoding is bad, mmkay?
(cherry picked from commit ed83a35fbeeb7f9005fe4792225fb50700791c6f)

src/server/game/AI/ScriptedAI/ScriptedCreature.cpp

@@ -539,7 +539,11 @@ void BossAI::UpdateAI(uint32 diff)
         return;
 
     while (uint32 eventId = events.ExecuteEvent())
+    {
         ExecuteEvent(eventId);
+        if (me->HasUnitState(UNIT_STATE_CASTING))
+            return;
+    }
 
     DoMeleeAttackIfReady();
 }
@@ -620,7 +624,11 @@ void WorldBossAI::UpdateAI(uint32 diff)
         return;
 
     while (uint32 eventId = events.ExecuteEvent())
+    {
         ExecuteEvent(eventId);
+        if (me->HasUnitState(UNIT_STATE_CASTING))
+            return;
+    }
 
     DoMeleeAttackIfReady();
 }