IPAddress: Use BinaryPrimitives.ReverseEndianness (#26329)

Author: justinvp

src/System.Net.Primitives/src/System/Net/IPAddress.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Buffers.Binary;
 using System.Diagnostics;
 using System.Net.Sockets;
 using System.Runtime.CompilerServices;
@@ -398,36 +399,17 @@ public bool TryFormat(Span<char> destination, out int charsWritten)
 
         public static long HostToNetworkOrder(long host)
         {
-#if BIGENDIAN
-            return host;
-#else
-            ulong value = (ulong)host;
-            value = (value << 32) | (value >> 32);
-            value = (value & 0x0000FFFF0000FFFF) << 16 | (value & 0xFFFF0000FFFF0000) >> 16;
-            value = (value & 0x00FF00FF00FF00FF) << 8 | (value & 0xFF00FF00FF00FF00) >> 8;
-            return (long)value;
-#endif
+            return BitConverter.IsLittleEndian ? BinaryPrimitives.ReverseEndianness(host) : host;
         }
 
         public static int HostToNetworkOrder(int host)
         {
-#if BIGENDIAN
-            return host;
-#else
-            uint value = (uint)host;
-            value = (value << 16) | (value >> 16);
-            value = (value & 0x00FF00FF) << 8 | (value & 0xFF00FF00) >> 8;
-            return (int)value;
-#endif
+            return BitConverter.IsLittleEndian ? BinaryPrimitives.ReverseEndianness(host) : host;
         }
 
         public static short HostToNetworkOrder(short host)
         {
-#if BIGENDIAN
-            return host;
-#else
-            return unchecked((short)((((int)host & 0xFF) << 8) | (int)((host >> 8) & 0xFF)));
-#endif
+            return BitConverter.IsLittleEndian ? BinaryPrimitives.ReverseEndianness(host) : host;
         }
 
         public static long NetworkToHostOrder(long network)