AutoCRUD theme update for Vaadin 25

Currently the AutoCRUD component assumes the Lumo theme is always used. In Vaadin 25, Vaadin components will get new base styles (i.e., no theme) and a new theme, Aura.

The AutoCRUD component, and the AutoForm and AutoGrid components within it, should ideally support the base styles versions, but at least the Aura theme.

