Make Marvin use RNG.Fill

Author: bartonjs

src/Common/src/System/Marvin.cs

@@ -107,12 +107,9 @@ private static uint _rotl(uint value, int shift)
 
         private static ulong GenerateSeed()
         {
-            using (RandomNumberGenerator rng = RandomNumberGenerator.Create())
-            {
-                var bytes = new byte[sizeof(ulong)];
-                rng.GetBytes(bytes);
-                return BitConverter.ToUInt64(bytes, 0);
-            }
+            Span<byte> bytes = stackalloc byte[sizeof(ulong)];
+            RandomNumberGenerator.Fill(bytes);
+            return BitConverter.ToUInt64(bytes);
         }
     }
 }