Currently, in order to see what's schedule will be run, I need to run schedule:list and eyeball the list to find the relevant ones.
This PR adds an option to sort the list by the next due date.

Before:
```
php artisan schedule:list

  0    *   * * *    php artisan command-one .......... Next Due: 55 minutes from now
  15   *   * * *    php artisan command-three ........ Next Due: 10 minutes from now
  17   *   * * *    php artisan command-two .......... Next Due: 12 minutes from now
```

After:
```
php artisan schedule:list

  15   *   * * *    php artisan command-three ........ Next Due: 10 minutes from now
  17   *   * * *    php artisan command-two .......... Next Due: 12 minutes from now
  0    *   * * *    php artisan command-one .......... Next Due: 55 minutes from now
```