Add parallel NPC steering back in (#13159)

Content.Server/NPC/HTN/HTNSystem.cs

@@ -61,6 +61,20 @@ public sealed class HTNSystem : EntitySystem
 
     private void OnLoad()
     {
+        // Clear all NPCs in case they're hanging onto stale tasks
+        foreach (var comp in EntityQuery<HTNComponent>(true))
+        {
+            comp.PlanningToken?.Cancel();
+            comp.PlanningToken = null;
+
+            if (comp.Plan != null)
+            {
+                var currentOperator = comp.Plan.CurrentOperator;
+                currentOperator.Shutdown(comp.Blackboard, HTNOperatorStatus.Failed);
+                comp.Plan = null;
+            }
+        }
+
         // Add dependencies for all operators.
         // We put code on operators as I couldn't think of a clean way to put it on systems.
         foreach (var compound in _prototypeManager.EnumeratePrototypes<HTNCompoundTask>())

Content.Server/NPC/Systems/NPCSteeringSystem.cs

@@ -204,12 +204,19 @@ namespace Content.Server.NPC.Systems
 
             var npcs = EntityQuery<NPCSteeringComponent, ActiveNPCComponent, InputMoverComponent, TransformComponent>()
                 .ToArray();
-
-            foreach (var (steering, _, mover, xform) in npcs)
+            var options = new ParallelOptions
             {
+                MaxDegreeOfParallelism = _parallel.ParallelProcessCount,
+            };
+
+            Parallel.For(0, npcs.Length, options, i =>
+            {
+                var (steering, _, mover, xform) = npcs[i];
+
                 Steer(steering, mover, xform, modifierQuery, bodyQuery, xformQuery, frameTime);
                 steering.LastSteer = mover.CurTickSprintMovement;
-            }
+            });
+
 
             if (_subscribedSessions.Count > 0)
             {