std.Io: give File a nonblocking bit on Windows

This tracks whether it is a file opened in synchronous mode, or
something that supports APC.

This will be needed in order to know whether concurrent batch operations
on the file should return error.ConcurrencyUnavailable, or use APC to
complete the batch.

This patch also switches to using NtCreateFile directly in
std.Io.Threaded for dirCreateFile, as well as NtReadFile for
fileReadStreaming, making it handle files opened in synchronous mode as
well as files opened in asynchronous mode.

lib/std/Progress.zig

@@ -979,6 +979,7 @@ fn serializeIpc(start_serialized_len: usize, serialized_buffer: *Serialized.Buff
         if (main_parent == .unused) continue;
         const file: Io.File = .{
             .handle = main_storage.getIpcFd() orelse continue,
+            .flags = if (is_windows) .{ .nonblocking = true } else .{},
         };
         const opt_saved_metadata = findOld(file.handle, old_ipc_metadata_fds, old_ipc_metadata);
         var bytes_read: usize = 0;