* Sort Localization generation output
- When creating locales that were assumed from existing locales, the
file that is used is non-deterministic. This adds a sort to the iterator
to ensure that the same existing locale is used to generate the assumed
locale
- When generating material, cupertino and date localizations, the generated getters were not sorted. This
introduces an alphabetic sort
* remove main.dart.snapshot
* Add check for placeholders being an empty map
* Remove unnecessary properties from en_ES.arb in the stocks example
* Use getter instead of methods in the stocks example
* Fixed "annotating types for function expression parameters" lint issue from generated localizations delegate code
*Starting with arb files in lib/l10n, the tool creates the following by default:
1. An AppLocalizations class containing:
- an `AppLocalizationsDelegate`
- a `supportedLocales` property that returns a list of all supported locales.
- a `localizationsDelegate` property that returns a list containing this delegate along with `GlobalMaterialLocalizations.delegate`, `GlobalCupertinoLocalizations.delegate`, and `GlobalWidgetsLocalizations.delegate`.
2. One Dart `message_<locale>.dart` file for each arb file, as well as a `messages_all.dart` file that performs the locale message lookup. The tool infers the locale of each arb file from the @@Locale property or the arb file's name.
