Use a portable Vector3 broadcast reduction

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: tannergooding

src/libraries/System.Private.CoreLib/src/System/Numerics/Vector3.cs

@@ -6,7 +6,6 @@
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Runtime.Intrinsics;
-using System.Runtime.Intrinsics.X86;
 
 namespace System.Numerics
 {
@@ -988,18 +987,8 @@ public static float Sum(Vector3 value)
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         internal static Vector3 Sum(Vector128<float> value)
         {
-            // Preserve Z while forming <Y + X, Z, Z, Z>, then add <Z, Y + X, Y + X, Y + X>.
-            // This broadcasts the sum without an extra addition of zero; NaN payloads can differ by lane.
-            if (Sse.IsSupported)
-            {
-                Vector128<float> pair = Sse.Shuffle(value, value, 0xA9);
-                pair = Sse.AddScalar(pair, value);
-                return (pair + Sse.Shuffle(pair, pair, 0x01)).AsVector3();
-            }
-
-            Vector128<float> sum = Vector128.Shuffle(value, Vector128.Create(1, 2, 2, 2));
-            sum = sum.WithElement(0, sum.ToScalar() + value.ToScalar());
-            return (sum + Vector128.Shuffle(sum, Vector128.Create(1, 0, 0, 0))).AsVector3();
+            Vector128<float> sum = Vector128.Shuffle(value, Vector128.Create(1, 0, 3, 2)) + value;
+            return Vector128.Create((Vector128.Shuffle(value, Vector128.Create(2)) + sum).ToScalar()).AsVector3();
         }
 
         /// <summary>Transforms a vector by a specified 4x4 matrix.</summary>