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.Shared/Atmos/Monitor/AtmosAlarmThreshold.cs

@@ -388,9 +388,21 @@ public enum AtmosMonitorLimitType //<todo.eoin Very similar to the above...
 // fields you can find this prototype in
 public enum AtmosMonitorThresholdType
 {
-    Temperature,
-    Pressure,
-    Gas
+    Temperature = 0,
+    Pressure = 1,
+    Gas = 2
+}
+
+/// <summary>
+/// Bitflags version of <see cref="AtmosMonitorThresholdType"/>
+/// </summary>
+[Flags]
+public enum AtmosMonitorThresholdTypeFlags
+{
+    None = 0,
+    Temperature = 1 << 0,
+    Pressure = 1 << 1,
+    Gas = 1 << 2,
 }
 
 [Serializable, NetSerializable]