Add OnNearbyTurretsScan hook

[WheteThunger]

object OnNearbyTurretsScan(AutoTurret turret, List<AutoTurret> nearbyTurrets, bool created)
{
    LogWarning($"OnNearbyTurretsScan works!");
    return null;
}

• Called when an auto turret spawns or despawns, in order to determine which turrets are nearby
• Returning non-null will cancel the default Vis.Entities call, allowing for an alternative searching implementation
• The list that will be populated with the Vis.Entities call is passed to the hook, so plugins can simply use a void return type and add additional turrets that may not be found by the Vis.Entities call, such as turrets that don't have a collider on the Deployed layer (e.g., for Car Turrets or Drone Turrets)
• Works similar to the OnSamSiteTargetScan hook