Implements some micro-optimizations

PkmnLib.Static/Utils/Random.cs

@@ -107,4 +107,21 @@ public class RandomImpl : IRandom
             throw new ArgumentException("List cannot be empty.", nameof(list));
         return list[GetInt(list.Count)];
     }
+
+    /// <summary>
+    /// Generates a new random <see cref="Guid"/>.
+    /// </summary>
+    /// <remarks>
+    /// The goal of this method is to create a new unique identifier that can be used for various purposes,
+    /// without having to rely on the system's built-in GUID generation. The built-in GUID generation
+    /// can be slow (see also: https://github.com/dotnet/runtime/issues/13628)
+    /// </remarks>
+    public Guid NewGuid()
+    {
+        var guidBytes = GuidCache.Value.AsSpan();
+        _random.NextBytes(guidBytes);
+        return new Guid(guidBytes);
+    }
+
+    private static readonly ThreadLocal<byte[]> GuidCache = new(() => new byte[16]);
 }