fix: Fixes spawner timer deserialization, decimal deserialization, and adds potion keg reverse lookup (#1711)

### Summary
* Fixes spawner timer deserialization
* Adds a check for a null timer and allows the timer to get recreated
* Adds PotionKeg reverse lookup
* Heavily optimizes decimal serialize/deserialize

Projects/Server.Tests/Tests/Serialization/DecimalSerializationTests.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Buffers.Binary;
+using System.Runtime.InteropServices;
+using Xunit;
+
+namespace Server.Tests;
+
+public class DecimalSerializationTests
+{
+    private static void Write(byte[] buffer, decimal value)
+    {
+        Span<int> bytes = stackalloc int[sizeof(decimal) / 4];
+        decimal.GetBits(value, bytes);
+
+        MemoryMarshal.Cast<int, byte>(bytes).CopyTo(buffer.AsSpan());
+    }
+
+    private static int ReadInt(ReadOnlySpan<byte> buffer) => BinaryPrimitives.ReadInt32LittleEndian(buffer);
+
+    private static decimal ReadDecimal(ReadOnlySpan<byte> buffer) => new(stackalloc int[4] { ReadInt(buffer), ReadInt(buffer[4..]), ReadInt(buffer[8..]), ReadInt(buffer[12..]) });
+
+    public static TheoryData<decimal> Data =>
+        new()
+        {
+            123.46m,
+            0.0256m,
+            10000m,
+            2m,
+            0.0001m,
+            0.0000000000000000000000000001m
+        };
+
+    [Theory]
+    [MemberData(nameof(Data))]
+    public void TestSerializeDecimal(decimal value)
+    {
+        // Arrange
+        byte[] buffer = new byte[sizeof(decimal)];
+
+        // Act
+        Write(buffer, value);
+
+        // Assert
+        Assert.Equal(value, ReadDecimal(buffer));
+    }
+}