[Performance] Improvements to ScanCloseMobs logic (#4534)

* [Performance] Minor improvements to ScanCloseMobs

* Remove timer checks one level up to reduce branching

* Reserve memory in m_close_mobs to avoid frequent re-allocations if not already reserved.

zone/client_packet.cpp

@@ -5013,7 +5013,11 @@ void Client::Handle_OP_ClientUpdate(const EQApplicationPacket *app) {
 	SetMoving(!(cy == m_Position.y && cx == m_Position.x));
 
 	CheckClientToNpcAggroTimer();
-	CheckScanCloseMobsMovingTimer();
+
+	if (m_mob_check_moving_timer.Check()) {
+		CheckScanCloseMobsMovingTimer();
+	}
+
 	CheckSendBulkClientPositionUpdate();
 
 	int32 new_animation = ppu->animation;