[Translations] Observe ICU support

[Guite]

• ICU - Main topic php-translation/symfony-bundle#399
• [Translation] %parameters% are not replaced when file is first dumped as +intl-icuand then read symfony/symfony#35328

The ICU message format is a different format than Symfony's one. Where Symfony's format uses percentage signs for placeholders (%placeholder%), ICU uses brackets ({placeholder}).

• https://symfony.com/doc/current/translation/message_format.html#message-placeholders