[MM-15296] Migrate "Preference.Save" to Sync by default (#10866)

* response format changes

* Generated mocks
Fixed all references of Preferences.Save

* Remove old code from store.go (incorrect merge)

* Review change - Add validations on count and error

* Review change - return from root level

* Review change - return 0 as nil value for int

* fix initialisation of err in preference_store

app/oauth.go

@@ -186,8 +186,8 @@ func (a *App) AllowOAuthAppAccessToUser(userId string, authRequest *model.Author
 		Value:    authRequest.Scope,
 	}
 
-	if result = <-a.Srv.Store.Preference().Save(&model.Preferences{authorizedApp}); result.Err != nil {
-		mlog.Error(result.Err.Error())
+	if _, err = a.Srv.Store.Preference().Save(&model.Preferences{authorizedApp}); err != nil {
+		mlog.Error(err.Error())
 		return authRequest.RedirectUri + "?error=server_error&state=" + authRequest.State, nil
 	}