Access lang maps

[Judimax]

• [UPDATE] Added new translation loader imports in flutter_i18n.dart: local_translation_loader, namespace_file_translation_loader, network_file_translation_loader, and translation_cache.
• [UPDATE] Updated FlutterI18n class to use the new translationCache for setting and getting locale data.
• [UPDATE] Introduced new methods in FlutterI18n class for handling locale maps and fetching values based on keys, supporting nested structures.
• [NEW] Added TranslationCache class to handle caching of translation data.
• [UPDATE] Updated pubspec.yaml to include mockito and build_runner as development dependencies.
• [NEW] Added new test cases in flutter_i18n_test.dart to test the getLocaleMap functionality and getValueFromKey method.
• [NEW] Created flutter_i18n_test.mocks.dart for generated mocks used in testing.
• [NEW] Added translation_cache_test.dart to test the functionality of the new TranslationCache class.

[ilteoood]

To avoid conflicts, re-open this when the other PR will be merged.