Refactor calendar constructor roundtrip tests to be per-calendar or use test_all_cals

Based on the discussion in PR #7899, the centralized tests in `components/calendar/src/tests/constructor_roundtrip.rs` should be refactored. Current state: All tests are in a single file, which might get out of sync with new calendar implementations. Proposed solutions: 1. Move unit tests into each individual calendar file, importing the shared Rata Die generation if possible. 2. Refactor to use `test_all_cals` with type-level conditionals to automatically test all calendars. This will help ensure that tests remain complete and close to the source code they are testing.