Add utility AI (#806)

Co-authored-by: Pieter-Jan Briers <pieterjan.briers@gmail.com>
Co-authored-by: Metal Gear Sloth <metalgearsloth@gmail.com>
Co-authored-by: Pieter-Jan Briers <pieterjan.briers+git@gmail.com>

Content.Server/AI/Utility/ExpandableActions/ExpandableUtilityAction.cs

@@ -0,0 +1,18 @@
+using System.Collections.Generic;
+using Content.Server.AI.Utility.Actions;
+using Content.Server.AI.WorldState;
+
+namespace Content.Server.AI.Utility.ExpandableActions
+{
+    /// <summary>
+    /// Expands into multiple separate utility actions for consideration, e.g. 5 nearby weapons 5 different actions
+    /// Ideally you would use the cached states for this
+    /// </summary>
+    public abstract class ExpandableUtilityAction : IAiUtility
+    {
+        public abstract float Bonus { get; }
+
+        // e.g. you may have a "PickupFood" action for all nearby food sources if you have the "Hungry" BehaviorSet.
+        public abstract IEnumerable<UtilityAction> GetActions(Blackboard context);
+    }
+}