support configuring default sorting/order (incl. eager-loaded edges)

[lrstanley]

Example:

func (Pet) Annotations() []schema.Annotation {
	return []schema.Annotation{
		entrest.WithDefaultSort("name"),
		entrest.WithDefaultOrder(entrest.OrderAsc),
	}
}

Also allowing eager-loaded edges, which aren't currently filterable (or allow special sorting) to be sorted in a standardized way.