terminal-util: port some generic code over to rearrange_stdio()

src/basic/fd-util.h

@@ -102,3 +102,7 @@ int acquire_data_fd(const void *data, size_t size, unsigned flags);
 int fd_move_above_stdio(int fd);
 
 int rearrange_stdio(int original_input_fd, int original_output_fd, int original_error_fd);
+
+static inline int make_null_stdio(void) {
+        return rearrange_stdio(-1, -1, -1);
+}