[Dot Shorthands] All tests in `tests/language` and co19 are passing.

[kallentu]

• [Dot Shorthands] Add co19 tests for "static access shorthand" feature co19#2976
• [Dot Shorthands] Language Tests in tests/language #57038

Test Tracker

https://docs.google.com/spreadsheets/d/19L0AhfQjS4VjvkdQ1lz61SZhK_nGjuPzs6OODEUyPx0/edit?usp=sharing&resourcekey=0-UwYFyigOGgtphjW50XztsQ

Test Status

https://dart-current-results.web.app/#/filter=language/enum_shorthands&showAll
https://dart-current-results.web.app/#/filter=co19/LanguageFeatures/Static-access-shorthand

[kallentu]

Beyond the tests that don't have anything to do with core dot shorthands implementation, all language and co19 tests are passing.