Ensuring smart_date works for all versions of Drupal 10 and 11

At MidCamp a few weeks ago, Martin Anderson-Clutz tapped me on the shoulder to check out a Smart Date issue for compatibility with Drupal 10.2. As of Drupal 10.2, ListItemBase::extractAllowedValues takes an array as its first argument versus a string. The method used to explode a newline separated string into an array for its callers. I took a look at the issue.