Multipe payment type methods show after continuing with the PayPal checkout Express Button

Problem/Motivation

Currently, when using one of the PayPal express checkout buttons, after confirming all of paypal's requests the user gets sent back to the "Order information" Page. If the "Payment information" pane is configured to show up on this page, the user can once again select their payment method type, if multiple payment method types are configured (e.g. using commerce_stripe and commerce_paypal).

This will lead to confusion by the end user.

Steps to reproduce

1. Setup both "commerce_paypal" and "commerce_stripe" to use the same checkout flow.
2. Press the EC-Button and proceed on PayPal's site.
3. After redirection, the stripe payment option is shown, even if the user already authorized their payment using PayPal.:

Proposed resolution

The payment method type checkboxes should become unclickable.

Remaining tasks

User interface changes

API changes

Data model changes