Core/Commands: Fix .cheat kill and add instakill immunity to it

Closes #7586

src/server/game/Entities/Unit/Unit.cpp

@@ -541,6 +541,10 @@ uint32 Unit::DealDamage(Unit* victim, uint32 damage, CleanDamage const* cleanDam
     if (IsAIEnabled)
         GetAI()->DamageDealt(victim, damage, damagetype);
 
+    if (victim->GetTypeId() == TYPEID_PLAYER)
+        if (victim->ToPlayer()->GetCommandStatus(CHEAT_GOD))
+            return 0;
+
     // Signal to pets that their owner was attacked
     if (victim->GetTypeId() == TYPEID_PLAYER)
     {

src/server/game/Spells/SpellEffects.cpp

@@ -277,6 +277,10 @@ void Spell::EffectInstaKill(SpellEffIndex /*effIndex*/)
     if (!unitTarget || !unitTarget->isAlive())
         return;
 
+    if (unitTarget->GetTypeId() == TYPEID_PLAYER)
+        if (unitTarget->ToPlayer()->GetCommandStatus(CHEAT_GOD))
+            return;
+
     if (m_caster == unitTarget)                              // prevent interrupt message
         finish();