Support all funding sources for PayPal Checkout

Problem/Motivation

The list of funding sources for PayPal Checkout should be updated / added as of this list: https://developer.paypal.com/sdk/js/configuration/#enable-funding

Here we go:

    'paypal' => t('PayPal'),
    'card' => t('Credit or debit card'),
    'credit' => t('PayPal Credit'),
    'paylater' => t('Pay Later'),
    'bancontact' => t('Bancontact'),
    'blik' => t('BLIK'),
    'eps' => t('eps'),
    'Giropay' => t('giropay'),
    'ideal' => t('iDEAL'),
    'mercadopago' => t('Mercado Pago'),
    'mybank' => t('MyBank'),
    'p24' => t('Przelewy24'),
    'sepa' => t('SEPA-Lastschrift'),
    'sofort' => t('Sofort'),
    'venmo' => t('Venmo'),

Waiting for MR's to become alive again, perhaps I'll create a patch earlier.
For 7.x-2.x you can find the implementation here soon: #3319545: Add option to explicitly enable funding sources

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes