Stock level is not correctly showing on the edit variation form

Our product variation stock level is not correctly showing on the product variation edit form. It displays 0 all the time, while the stock is correctly shown if we show the stock level field in a view.

Correct

Wrong

In `StockLevelWidgetBase.php` the current level is retrieved with `$level = $field->get('available_stock')->getValue();`. I think we can better use the `StockServiceManager` here to get the actual stock level of the variation?