i18n Improvements (#47174)
This serves to correct a specific issue related to multiple locales being specified in the pathname as well as some general i18n improvements.
- Multiple locales are now parsed correctly (only taking the first locale, treating the rest of the string as the pathname)
- `LocaleRouteNormalizer` has been split into `I18NProvider` and `LocaleRouteNormalizer` (tests added)
- Adjusted the `I18NProvider.analyze` method (previously `LocaleRouteNormalizer.match`) to require the `defaultLocale: string | undefined` to ensure consistent behaviour
- Added more comments around i18n
