[Checkout] Offer a single way to proceed to Checkout

Problem reported: Most of the time the product page is too cluttered with many checkout and quick checkout options, such as Apple Pay, Shop Pay, PayPal etc., adding too much cognitive load.

The hypothesis is that by displaying only one checkout method (CHECKOUT NOW), the visitor will be able to advance to checkout with minimal mental effort, having later (on the Checkout page), access to all the quick checkout methods if needed.