Optimizations from server profile (#38290)

* Properly cache regexes in chat sanitization/accents

Wow I wonder if `new Regex()` has a cost to it *looks at server profile*.

* Avoid lag caused by Tippy command completions

CompletionHelper.PrototypeIDs explicitly says *not* to use it with EntityPrototype. Unsurprisingly, reporting a completion result for every entity prototype in the game is a *bad idea*.

* Add active count metrics to some high-load systems

Mover & NPCs

I suspect the thing that caused the Leviathan round to shit itself on performance is NPC spam in space or something. So let's verify that.

* Enable parallel processing on pow3r again

Originally disabled due to a theory of it causing bugs, it was re-enabled on Vulture, and I'm not aware of it having caused any issues there.

* Replace hashset with bitflags for AtmosMonitor alert types.

Allocating these hashsets was like 20% of the CPU of atmos, somehow.

* Cache HashSet used for space movement collider checks

Turns out this was a ton of server allocations. Huh.

Content.Server/NPC/Systems/NPCSteeringSystem.cs

@@ -30,11 +30,16 @@ using Robust.Shared.Timing;
 using Robust.Shared.Utility;
 using Content.Shared.Prying.Systems;
 using Microsoft.Extensions.ObjectPool;
+using Prometheus;
 
 namespace Content.Server.NPC.Systems;
 
 public sealed partial class NPCSteeringSystem : SharedNPCSteeringSystem
 {
+    private static readonly Gauge ActiveSteeringGauge = Metrics.CreateGauge(
+        "npc_steering_active_count",
+        "Amount of NPCs trying to actively do steering");
+
     /*
      * We use context steering to determine which way to move.
      * This involves creating an array of possible directions and assigning a value for the desireability of each direction.
@@ -87,6 +92,8 @@ public sealed partial class NPCSteeringSystem : SharedNPCSteeringSystem
 
     private object _obstacles = new();
 
+    private int _activeSteeringCount;
+
     public override void Initialize()
     {
         base.Initialize();
@@ -244,12 +251,15 @@ public sealed partial class NPCSteeringSystem : SharedNPCSteeringSystem
         };
         var curTime = _timing.CurTime;
 
+        _activeSteeringCount = 0;
+
         Parallel.For(0, index, options, i =>
         {
             var (uid, steering, mover, xform) = npcs[i];
             Steer(uid, steering, mover, xform, frameTime, curTime);
         });
 
+        ActiveSteeringGauge.Set(_activeSteeringCount);
 
         if (_subscribedSessions.Count > 0)
         {
@@ -324,6 +334,8 @@ public sealed partial class NPCSteeringSystem : SharedNPCSteeringSystem
             return;
         }
 
+        Interlocked.Increment(ref _activeSteeringCount);
+
         var agentRadius = steering.Radius;
         var worldPos = _transform.GetWorldPosition(xform);
         var (layer, mask) = _physics.GetHardCollision(uid);