[PM-6769] [SM-1158] Fix Translation pipe issues on main (#8319)

* Require init in i18n service.

this is needed to load translations and set translation locale

* No longer need to cast i18n

* Expose user preferred locale in i18nService

This is for correctly displaying `default` when no locale has been set in preferences components. The `locale$` observable should always resolve to the currently locale currently being translated to.

apps/browser/src/popup/services/init.service.ts

@@ -26,6 +26,7 @@ export class InitService {
   init() {
     return async () => {
       await this.stateService.init();
+      await this.i18nService.init();
 
       if (!BrowserPopupUtils.inPopup(window)) {
         window.document.body.classList.add("body-full");