Airlock / firelock code refactor, pseudo-prediction implementation (#3037)

* splits off airlocks, firelocks

* adds airlock prediction. anims broken though

* fixes animation weirdness

* removes opacity prediction because it looked odd

* Now firelocks don't visually start open. Argh.

* Fixes firelock weirdness, saneifies _state var.

* Documentation changes, code shuffle.

* Lets firelocks crush people.

* Stops open-hand opening/closing firelocks.

* updates serializable, netserializable attributes

* Addresses reviews... hopefully.

* updates submodule?

* nullability

* fuck fuck fuck fuck

* fucking finally

Content.Shared/GameObjects/ContentNetIDs.cs

@@ -1,4 +1,4 @@
-namespace Content.Shared.GameObjects
+namespace Content.Shared.GameObjects
 {
     // Starting from 1000 to avoid crossover with engine.
     public static class ContentNetIDs
@@ -91,6 +91,8 @@
         public const uint DAMAGEABLE = 1084;
         public const uint MAGBOOTS = 1085;
         public const uint TAG = 1086;
+        // Used for clientside fake prediction of doors.
+        public const uint DOOR = 1087;
 
         // Net IDs for integration tests.
         public const uint PREDICTION_TEST = 10001;