Add UI for fallback_formatter settings

- [x] Add fallback_formatter_field_formatter_settings_form
- [x] Add fallback_formatter_field_formatter_settings_summary
- [x] Fix vertical tabs inside formatter settings form


My initial thoughts:
- Needs to have a table select so the user can select which formatters are enabled
- Needs to have a tabledrag so the user can select the order of formatters
- Needs to expose the options for enabled formatters