WIP Make networking code thread-safe and refactor update ID

Replaces direct increments of LastClientListUpdateID with a thread-safe IncrementLastClientListUpdateID method and uses Interlocked for atomic operations. Refactors EntitySpawner to lock access to the spawn/remove queue for thread safety. Updates INetSerializableStruct to use concurrent collections for cached variables and type behaviors, improving thread safety in networking code.

Barotrauma/BarotraumaShared/SharedSource/Networking/NetworkMember.cs

@@ -1,6 +1,7 @@
 using Microsoft.Xna.Framework;
 using System;
 using System.Collections.Generic;
+using System.Threading;
 
 namespace Barotrauma.Networking
 {
@@ -186,10 +187,19 @@ namespace Barotrauma.Networking
     {
         protected const int MaxSubNameLengthInErrorMessages = 16;
 
+        private int lastClientListUpdateID;
         public UInt16 LastClientListUpdateID
         {
-            get;
-            set;
+            get => (UInt16)Interlocked.CompareExchange(ref lastClientListUpdateID, 0, 0);
+            set => Interlocked.Exchange(ref lastClientListUpdateID, value);
+        }
+
+        /// <summary>
+        /// Thread-safe increment of LastClientListUpdateID
+        /// </summary>
+        public void IncrementLastClientListUpdateID()
+        {
+            Interlocked.Increment(ref lastClientListUpdateID);
         }
 
         public abstract bool IsServer { get; }