[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/command_expand_collapse.go

@@ -68,7 +68,7 @@ func (a *App) setCollapsePreference(args *model.CommandArgs, isCollapse bool) *m
 		Value:    strconv.FormatBool(isCollapse),
 	}
 
-	if result := <-a.Srv.Store.Preference().Save(&model.Preferences{pref}); result.Err != nil {
+	if _, err := a.Srv.Store.Preference().Save(&model.Preferences{pref}); err != nil {
 		return &model.CommandResponse{Text: args.T("api.command_expand_collapse.fail.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
 	}