I18N: Prevent incorrect language dropdown entries when there are .l10n.php files.

In [57516], the just-in-time translation loading logic was enhanced to support cases where only `.l10n.php` translation exist but no `.mo` or `.po` files. This caused a slight regression in `get_available_languages()`, which uses the list of files to populate the language dropdown list on the settings page.

To address this, the new file extension is now properly stripped off, and the resulting file list is de-duplicated. New test files are added to allow the existing tests to cover this new scenario.

See #59656.
Fixes #60553.

git-svn-id: https://develop.svn.wordpress.org/trunk@57639 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/data/languages/admin-en_GB.l10n.php

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+<?php
+return ['domain'=>NULL,'plural-forms'=>'nplurals=2; plural=n != 1;','messages'=>['Thank you for updating! WordPress %s makes your site more connected and responsive.'=>'Thank you for updating! WordPress %s makes your site more connected and responsive.','New %1$s, %2$s, and %3$s objects make interacting with terms, comments, and networks more predictable and intuitive in code.'=>'New %1$s, %2$s, and %3$s objects make interacting with terms, comments, and networks more predictable and intuitive in code.','Comment queries now have cache handling to improve performance. New arguments in %s make crafting robust comment queries simpler.'=>'Comment queries now have cache handling to improve performance. New arguments in %s make crafting robust comment queries simpler.','Term, comment, and network objects'=>'Term, comment, and network objects','Comment query improvements'=>'Comment query improvements'],'language'=>'en_GB','x-generator'=>'Poedit 1.8.10'];

tests/phpunit/data/languages/admin-es_ES.l10n.php

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+<?php
+return ['domain'=>NULL,'plural-forms'=>'nplurals=2; plural=n != 1;','messages'=>['Thank you for updating! WordPress %s makes your site more connected and responsive.'=>'¡Gracias por actualizar! WordPress %s hace que tu sitio esté más conectado y sea más adaptable.','New %1$s, %2$s, and %3$s objects make interacting with terms, comments, and networks more predictable and intuitive in code.'=>'Ahora los objetos %1$s, %2$s y %3$s hacen que interactuar con términos, comentarios y redes sea más predecible y que el código sea más intuitivo.','Comment queries now have cache handling to improve performance. New arguments in %s make crafting robust comment queries simpler.'=>'Las consultas de comentarios ahora tiene una caché que mejora el rendimiento. Nuevos argumentos en %s hacen que sea más fácil crear consultas robustas.','Term, comment, and network objects'=>'Objetos de término, comentario y red','Comment query improvements'=>'Mejoras en las consultas de comentarios'],'language'=>'es_ES','x-generator'=>'Poedit 1.8.10'];

tests/phpunit/data/languages/admin-network-en_GB.l10n.php

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+<?php
+return ['domain'=>NULL,'plural-forms'=>'nplurals=2; plural=n != 1;','messages'=>['A password reset link will be sent to the user via email.'=>'A password reset link will be sent to the user via email.','If registration is disabled, please set %1$s in %2$s to a URL you will redirect visitors to if they visit a non-existent site.'=>'If registration is disabled, please set %1$s in %2$s to a URL you will redirect visitors to if they visit a non-existent site.','Site users list'=>'Site users list','Site users list navigation'=>'Site users list navigation','Sites list'=>'Sites list'],'language'=>'en_GB','x-generator'=>'Poedit 1.8.10'];

tests/phpunit/data/languages/admin-network-es_ES.l10n.php

@@ -0,0 +1,2 @@
+<?php
+return ['domain'=>NULL,'plural-forms'=>'nplurals=2; plural=n != 1;','messages'=>['A password reset link will be sent to the user via email.'=>'Se te enviará un enlace por email para que puedas cambiar la contraseña.','If registration is disabled, please set %1$s in %2$s to a URL you will redirect visitors to if they visit a non-existent site.'=>'Si el registro de usuarios está desactivado , establece como valor de %1$s en %2$s una URL donde redirigir a los visitantes que accedan a un sitio inexistente.','Site users list navigation'=>'Navegación por la lista de usuarios del sitio','Site users list'=>'Lista de usuarios del sitio','Sites list navigation'=>'Navegación por la lista de sitios'],'language'=>'es_ES','x-generator'=>'Poedit 1.8.10'];

tests/phpunit/data/languages/continents-cities-es_ES.l10n.php

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+<?php
+return ['domain'=>NULL,'plural-forms'=>'nplurals=2; plural=n != 1;','messages'=>['Vincennes'=>'Vincennes','Winamac'=>'Winamac','Inuvik'=>'Inuvik','Iqaluit'=>'Iqaluit','Jamaica'=>'Jamaica'],'language'=>'es_ES','x-generator'=>'Poedit 1.8.10'];

tests/phpunit/data/languages/de_DE.l10n.php

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+<?php
+return ['domain'=>NULL,'plural-forms'=>'nplurals=2; plural=n != 1;','messages'=>['html_lang_attribute'=>'de-DE','text directionltr'=>'ltr','number_format_decimal_point'=>',','number_format_thousands_sep'=>'.','Update %s now'=>'Jetzt %s aktualisieren','[%1$s] Confirm Action: %2$s'=>'[%1$s] Aktion bestätigen: %2$s','[%s] Erasure Request Fulfilled'=>'[%s] Löschauftrag ausgeführt','[%s] Personal Data Export'=>'[%s] Export personenbezogener Daten'],'language'=>'de_DE','x-generator'=>'Poedit 2.2.1'];

tests/phpunit/data/languages/en_GB.l10n.php

@@ -0,0 +1,2 @@
+<?php
+return ['domain'=>NULL,'plural-forms'=>'nplurals=2; plural=n != 1;','messages'=>['text directionltr'=>'ltr','<strong>ERROR</strong>: Sorry, that username is not allowed.'=>'<strong>ERROR</strong>: Sorry, that username is not allowed.','Invalid parameter.'=>'Invalid parameter.','menu location(Current: %s)'=>'(Current: %s)','menu(Currently set to: %s)'=>'(Currently set to: %s)'],'language'=>'en_GB','x-generator'=>'Poedit 1.8.10'];

tests/phpunit/data/languages/es_ES.l10n.php

@@ -0,0 +1,2 @@
+<?php
+return ['domain'=>NULL,'plural-forms'=>'nplurals=2; plural=n != 1;','messages'=>['text directionltr'=>'ltr','<strong>ERROR</strong>: Sorry, that username is not allowed.'=>'<strong>ERROR</strong>: Lo siento, ese nombre de usuario no está permitido.','Invalid parameter.'=>'Parámetro no válido. ','menu location(Current: %s)'=>'(Actual: %s)','menu(Currently set to: %s)'=>'(Actualmente fijado en: %s)','[%1$s] Confirm Action: %2$s'=>'[%1$s] Confirmar la acción: %2$s','[%s] Erasure Request Fulfilled'=>'[%s] Solicitud de borrado completada','[%s] Personal Data Export'=>'[%s] Exportación de datos personales'],'language'=>'es_ES','x-generator'=>'Poedit 2.3'];

tests/phpunit/data/languages/ja_JP.l10n.php

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+<?php
+return ['domain'=>NULL,'plural-forms'=>'nplurals=2; plural=n != 1;','messages'=>['html_lang_attribute'=>'ja','text directionltr'=>'ltr','number_format_decimal_point'=>'number_format_decimal_point','number_format_thousands_sep'=>'number_format_thousands_sep','Update %s now'=>'今すぐ %s を更新','Word count type. Do not translate!words'=>'characters_including_spaces','excerpt_length55'=>'110','comment_excerpt_length20'=>'40','draft_length10'=>'40'],'language'=>'ja_JP','x-generator'=>'Poedit 1.8.10'];