The dev/tools/localizations/bin/gen_date_localizations.dart script needs to be run whenever there are updates to the ICU data that's being used by intl or whenever we add new locale to Flutter. However, since this hasn't been done in awhile, the code has gone stale and I had to make a separate PR #124547 to fix the outdated parts.

We should write a test that checks that gen_date_localizations.dart isn't broken by other parts of the code base, and also find a good way to run it on CI to check if it needs to be run again.