Fix newPosition calculation in PositionStream method

Updated the PositionStream method in UsingMemoryStreamSlim.ReadWrite.cs to handle cases where maxPosition is zero. Previously, newPosition was assigned a random integer within the range of maxPosition, which could lead to errors when maxPosition was zero. Now, newPosition is set to zero if maxPosition is zero, ensuring correct behavior.

Source/Tst/Shared/KZDev.PerfUtils.MemoryStreamSlim.Tests.Shared/UsingMemoryStreamSlim.ReadWrite.cs

@@ -1131,7 +1131,7 @@ void WriteByteDataToStream (MemoryStreamSlim stream, byte[] dataCopyArray, ref i
 
             void PositionStream (MemoryStreamSlim stream, int maxPosition, out int dataCopyArrayPosition)
             {
-                int newPosition = RandomSource.GetRandomInteger(maxPosition);
+                int newPosition = (0 == maxPosition) ? 0 : RandomSource.GetRandomInteger(maxPosition);
                 stream.Position = dataCopyArrayPosition = newPosition;
             }