Fluid spread refactor (#11908)

Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>
Fix undefined

Content.Shared/SharedArrayExtension.cs

@@ -0,0 +1,28 @@
+using Robust.Shared.Random;
+
+namespace Content.Shared;
+
+public static class SharedArrayExtension
+{
+    /// <summary>
+    /// Randomizes the array mutating it in the process
+    /// </summary>
+    /// <param name="array">array being randomized</param>
+    /// <param name="random">source of randomization</param>
+    /// <typeparam name="T">type of array element</typeparam>
+    public static void Shuffle<T>(this Span<T> array, IRobustRandom? random = null)
+    {
+        var n = array.Length;
+        if (n <= 1)
+            return;
+        IoCManager.Resolve(ref random);
+
+        while (n > 1)
+        {
+            n--;
+            var k = random.Next(n + 1);
+            (array[k], array[n]) =
+                (array[n], array[k]);
+        }
+    }
+}