Add readonly where it is missing and fix those field names according to their modifiers (#2589)

Content.Server/AI/WorldState/BlackboardManager.cs

@@ -14,7 +14,7 @@ namespace Content.Server.AI.WorldState
     {
         // Cache the known types
         public IReadOnlyCollection<Type> AiStates => _aiStates;
-        private List<Type> _aiStates = new List<Type>();
+        private readonly List<Type> _aiStates = new List<Type>();
 
         public void Initialize()
         {
@@ -24,8 +24,8 @@ namespace Content.Server.AI.WorldState
             {
                 _aiStates.Add(state);
             }
-            
+
             DebugTools.AssertNotNull(_aiStates);
         }
     }
-}
+}