Update Chinese language support (#7878)

* Rename zh_hant to zh_Hant

* Fix front-end language mappings

* Remove "zh" code (is "zh_Hans")

* Remap backend translations

* Update frontend translation files

* Fix locale spec for front-end

* Update pt_BR for frontend translations

* Fix pt_BR for backend

* Rename es-mx to es_MX

src/frontend/.linguirc

@@ -8,7 +8,7 @@
         "el",
         "en",
         "es",
-        "es-mx",
+        "es_MX",
         "et",
         "fa",
         "fi",
@@ -24,7 +24,7 @@
         "no",
         "pl",
         "pt",
-        "pt-br",
+        "pt_BR",
         "ro",
         "ru",
         "sk",
@@ -35,8 +35,8 @@
         "tr",
         "uk",
         "vi",
-        "zh-hans",
-        "zh-hant",
+        "zh_Hans",
+        "zh_Hant",
         "pseudo-LOCALE"],
     "catalogs": [{
         "path": "src/locales/{locale}/messages",