Core/Creatures: converted CMSG_PET_ACTION to packet class and moved most parts of it to the SummonInfo API

src/server/game/Spells/Spell.cpp

@@ -3710,10 +3710,9 @@ void Spell::_cast(bool skipCheck)
         return;
     }
 
-    if (Unit* unitCaster = m_caster->ToUnit())
-        if (m_spellInfo->HasAttribute(SPELL_ATTR1_DISMISS_PET_FIRST))
-            if (Creature* pet = ObjectAccessor::GetCreature(*m_caster, unitCaster->GetPetGUID()))
-                pet->DespawnOrUnsummon();
+    if (m_spellInfo->HasAttribute(SPELL_ATTR1_DISMISS_PET_FIRST))
+        if (Unit* unitCaster = m_caster->ToUnit())
+            unitCaster->DismissPet();
 
     PrepareTriggersExecutedOnHit();