[MM-60792] Add support for loading experimental (e.g., in progress) languages (#29009)

* Add support for loading experimental (e.g., in progress) languages

* Fix e2e config

* Improve language labels

* Improvements

webapp/platform/types/src/config.ts

@@ -58,6 +58,7 @@ export type ClientConfig = {
     EnableCustomEmoji: string;
     EnableCustomGroups: string;
     EnableCustomUserStatuses: string;
+    EnableExperimentalLocales: string;
     EnableUserStatuses: string;
     EnableLastActiveTime: string;
     EnableTimedDND: string;
@@ -720,6 +721,7 @@ export type LocalizationSettings = {
     DefaultServerLocale: string;
     DefaultClientLocale: string;
     AvailableLocales: string;
+    EnableExperimentalLocales: boolean;
 };
 
 export type SamlSettings = {