std.Io.net: add error.PortUnreachable to NetReceive

closes #31787

lib/std/Io.zig

@@ -374,6 +374,13 @@ pub const Operation = union(enum) {
             ConnectionResetByPeer,
             /// The local network interface used to reach the destination is offline.
             NetworkDown,
+            /// A connectionless packet was previously sent successfully,
+            /// however, it was not received because no service is operating at
+            /// the destination port of the transport on the remote system.
+            /// This caused an ICMP port unreachable packet to be returned to
+            /// the OS where it was queued up to be reported at the next call
+            /// to send or receive on the bound socket.
+            PortUnreachable,
         } || Io.UnexpectedError;
 
         pub const Result = struct { ?net.Socket.ReceiveError, usize };

lib/std/Io/Threaded.zig

@@ -13017,6 +13017,7 @@ fn netReceiveOneWindows(
         .CANCELLED => unreachable,
         .INSUFFICIENT_RESOURCES => return error.SystemResources,
         .BUFFER_OVERFLOW => return error.MessageOversize,
+        .PORT_UNREACHABLE => return error.PortUnreachable,
         else => |status| return windows.unexpectedStatus(status),
     }
 }