Core/Creatures: Improved movement interruption while casting spells

Port From (https://github.com/TrinityCore/TrinityCore/commit/cc57c9dad59a2eded2f7ea0471aa79c89b390559)

Source/Game/Entities/Unit/Unit.Spells.cs

@@ -1047,7 +1047,8 @@ namespace Game.Entities
 
             Spell spell = GetCurrentSpell(CurrentSpellTypes.Generic);
             if (spell != null)
-                if (CanCastSpellWhileMoving(spell.GetSpellInfo()))
+                if (CanCastSpellWhileMoving(spell.GetSpellInfo()) || spell.GetState() == SpellState.Finished ||
+                    !spell.m_spellInfo.InterruptFlags.HasFlag(SpellInterruptFlags.Movement))
                     return false;
 
             // channeled spells during channel stage (after the initial cast timer) allow movement with a specific spell attribute

Source/Game/Spells/Spell.cs

@@ -7809,6 +7809,12 @@ namespace Game.Spells
             if (IsTriggered())
                 return SpellCastResult.SpellCastOk;
 
+            // Creatures (not controlled) give priority to spell casting over movement.
+            // We assume that the casting is always valid and the current movement
+            // is stopped by Unit:IsmovementPreventedByCasting to prevent casting interruption.
+            if (m_caster.IsCreature() && !m_caster.ToCreature().IsControlledByPlayer())
+                return SpellCastResult.SpellCastOk;
+
             Unit unitCaster = m_caster.ToUnit();
             if (unitCaster != null)
             {