Product Rating block: Show "No reviews" label rather than empty starts when product has no reviews

[thealexandrelara]

When working on #9556, we made the decision to maintain the existing behavior found in the classic Single Product Template: hiding the product rating when there are no reviews. However, in the Editor, we opted to display empty stars when the merchant adds the block to a product that has no reviews. This is necessary to provide a visual representation for merchants when they add the block into a template, page, or post.

Current

Expected

The current behavior may lead to confusion as the presence of five faded stars could be misinterpreted as representing a zero average rating, rather than indicating a lack of ratings. To address this concern, @shaunandrews has suggested an alternative approach where we display a "No reviews" label instead. This solution aims to provide clearer and more intuitive information to merchants.