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/NPCSystem.cs

@@ -8,6 +8,7 @@ using Content.Shared.Mobs;
 using Content.Shared.Mobs.Systems;
 using Content.Shared.NPC;
 using Content.Shared.NPC.Systems;
+using Prometheus;
 using Robust.Server.GameObjects;
 using Robust.Shared.Configuration;
 using Robust.Shared.Player;
@@ -19,6 +20,10 @@ namespace Content.Server.NPC.Systems
     /// </summary>
     public sealed partial class NPCSystem : EntitySystem
     {
+        private static readonly Gauge ActiveGauge = Metrics.CreateGauge(
+            "npc_active_count",
+            "Amount of NPCs that are actively processing");
+
         [Dependency] private readonly IConfigurationManager _configurationManager = default!;
         [Dependency] private readonly HTNSystem _htn = default!;
         [Dependency] private readonly MobStateSystem _mobState = default!;
@@ -138,6 +143,8 @@ namespace Content.Server.NPC.Systems
 
             // Add your system here.
             _htn.UpdateNPC(ref _count, _maxUpdates, frameTime);
+
+            ActiveGauge.Set(Count<ActiveNPCComponent>());
         }
 
         public void OnMobStateChange(EntityUid uid, HTNComponent component, MobStateChangedEvent args)