fix(core): Adds SkipLocalsInitAttribute support, optimizes broadcasted packets (#363)

- [X] Adds support for `SkipLocalsInitAttribute`. SkipLocalsInitAttribute skips initializing stack variables including `stackalloc`. I don't think it is wired/working yet but should be implemented soon.
- [X] Optimizes broadcasted packets by checking if the first byte (packet ID) is non-zero. If it is already set, it reuses the buffer.
- [X] Removes unnecessary refs to Spans. I don't think the Span struct itself is mutable, so a ref is not helpful.

Projects/Server/Network/PacketUtilities.cs

@@ -40,9 +40,20 @@ namespace Server.Network
             writer.Seek(length, SeekOrigin.Begin);
         }
 
+        // If LOCAL INIT is off, then stack/heap allocations have garbage data
+        // Initializes the first byte (Packet ID) so it can be used as a flag.
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void InitializePacket(this Span<byte> buffer)
+        {
+#if NO_LOCAL_INIT
+            buffer[0] = 0;
+#endif
+        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static void InitializePackets(this Span<byte> buffer, int chunkLength)
         {
+#if NO_LOCAL_INIT
             var index = 0;
 
             while (index < buffer.Length)
@@ -50,6 +61,7 @@ namespace Server.Network
                 buffer[index] = 0;
                 index += chunkLength;
             }
+#endif
         }
     }
 }