update unit tests to check for presence of JSON files for all wp locales

let's add unit tests to confirm we have all needed files. at the moment, for example, get_cldr_locale() for the .org locale als returns gsw which is a valid CLDR language code but is one of the locales like pt-br which have a different language code than the locale they use for JSON files/trees ( 😡).

starting point that could be added to test_all_WordPress_locales():

        foreach ( $wp_locales as $wp_locale ) {
            $cldr_locale = $this->cldr->get_cldr_locale( $wp_locale );
            $this->assertNotEmpty( $cldr_locale );
            $cldr_json_file = dirname( __DIR__ ) . "/json/28.0.2/cldr-localenames-modern/main/$cldr_locale/territories.json";
            $this->assertFileExists( $cldr_json_file );
        }

but we don't want to have to update version number so probably call get_cldr_json_file() instead.

Automattic / wp-cldr

update unit tests to check for presence of JSON files for all wp locales #54