refactor(Core/Combat): Port TrinityCore heap-based threat system (#24715)

Co-authored-by: blinkysc <blinkysc@users.noreply.github.com>
Co-authored-by: Treeston <treeston.mmoc@gmail.com>
Co-authored-by: killerwife <killerwife@gmail.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/server/scripts/Kalimdor/TempleOfAhnQiraj/boss_ouro.cpp

@@ -270,7 +270,7 @@ struct boss_ouro : public BossAI
 
     void EnterEvadeMode(EvadeReason /*why*/) override
     {
-        if (me->GetThreatMgr().GetThreatList().empty())
+        if (me->GetThreatMgr().IsThreatListEmpty())
         {
             DoCastSelf(SPELL_OURO_SUBMERGE_VISUAL);
             me->DespawnOrUnsummon(1s);