Support localization of dynamic plugins

We need to support localization of dynamic plugins. The current proposal is to have one i18n namespace per dynamic plugin with a fixed name: `${plugin-name}-plugin`. Since console will know the list of plugins on startup, it can add these namespaces to the i18next config.

The console backend will need to implement an endpoint at the i18next load path. The endpoint will see if the namespace matches the known plugin namespaces. If so, it will proxy to the plugin. Otherwise it will serve the static file from the local filesystem.