[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

server/config/client.go

@@ -75,6 +75,8 @@ func GenerateClientConfig(c *model.Config, telemetryID string, license *model.Li
 	props["EnablePublicLink"] = strconv.FormatBool(*c.FileSettings.EnablePublicLink)
 
 	props["AvailableLocales"] = *c.LocalizationSettings.AvailableLocales
+	props["EnableExperimentalLocales"] = strconv.FormatBool(*c.LocalizationSettings.EnableExperimentalLocales)
+
 	props["SQLDriverName"] = *c.SqlSettings.DriverName
 
 	props["EnableEmojiPicker"] = strconv.FormatBool(*c.ServiceSettings.EnableEmojiPicker)