Migrate Time Slot field to Smart Date

[DrupalPhil]

Currently, we're using the date_range approach. This has issues:

1. Time is required if you add a date (feature requests for scheduling #246)
2. Because of 1, all-day events can't be made
3. The UX for admins is tough unless a bunch of custom JS is added to improve it (also feature requests for scheduling #246)

Enter, Smart Date:
https://www.drupal.org/project/smart_date

This could address all of those issues. This would require:

1. Adding the new Smart Date field
2. Migrating from the legacy field to the new field
3. Testing
4. Testing
5. Deployment
6. Testing
7. Delete legacy field
8. Testing

[DrupalPhil]

Let's push to 2027