feat(payment): STRIPE-25 create customer strategy for Stripe Upe link

[AlanMunozN]

What? STRIPE-25

Add StripeUpe customer strategy and adapt the logic to use only an instance of StripeUpeLoader.

Why?

Stripe wants to create the ability to use the Stripe Link experience, the experience includes using Stripe Iframe on Customer instead of BC component when the user is a Guest and the StripeLink toggle is activated on the StripeUpe payments setup.

Testing / Proof

PLEASE CHECK THE VIDEO TO UNDERSTAND MORE ABOUT THE APPROACH

VIDEO

Depends on

https://github.com/bigcommerce/checkout-js/pull/882

Dependency of

https://github.com/bigcommerce/bigpay-client-php/pull/253 https://github.com/bigcommerce/bigcommerce/pull/46265 https://github.com/bigcommerce/bigpay/pull/5359

Ping @bigcommerce/checkout @bigcommerce/payments @bigcommerce/apex-integrations