Add std::format test for the std::chrono calendar types:

• date: year_month_last, year_month_weekday, year_month_weekday_last
• building blocks:
  • weekday_indexed, weekday_last,
  • month_day, month_day_last,
  • month_weekday, month_weekday_last,
  • year_month

For date formatting we need to test values of computed specifiers (day of month, day of year). For building block types, they are not computed values, so !ok() values and single test may be sufficient.