After Dart VM change we are now required to use loadLibrary on an import whenever it is imported as deferred.

See: https://dart-review.googlesource.com/c/sdk/+/149613

Updated gen_missing_localizations to copy the english strings instead of using 'TBD' for other locales. (#57053)

* Run encode kn character encoding tool when gen_localizations is run

* Add test that ensures *_kn.arb files are properly encoded/escaped in order to be checked in

* Fix *_no.arb test to not incorrectly pass

* Fix breaking change introduced by gen_l10n output-dir option

* Add new output-dir option for gen_l10n tool

* Generate methods using template resources if they do not exist in other locales

* Added a flag to either output of messages that have not been translated with detail into a file, or display a summary on the terminal.

* Add integration test for fallback message usage

* [gen_l10n] Add scriptCode handling

Date Picker UI redesign

* Fix suppportedLocales list

* Refactor integration tests for gen_l10n tool to catch exceptions

* Expose --header and --header-file arguments for gen_l10n

* unnecessary escapes fixes

* replace some strings with raw strings

* update regexp

* address review comments

Added a new script to generate missing localizations for use when adding new localizations to the Flutter framework.