Add BLIK and MercadoPago as funding methods

[jorgeatorres]

Issue: #796

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Description

From the current list of alternative payment methods, we were missing both "BLIK" and "MercadoPago". This PR adds both options as funding methods and also sorts the dropdown options alphabetically, leaving only PayPal Credit and Debit/Credit Card at the top, as those are the ones more commonly used.

Steps to test:

1. Check out trunk.
2. Add an item to the cart and go to the checkout page.

3. Use the following snippet to temporarily change your site to PLN and your buyer country to Poland:

   add_filter( 'woocommerce_paypal_express_checkout_sdk_script_args', function( $args ) {
      $args['buyer-country'] = 'PL';
      return $args;
   } );
   
   add_filter( 'woocommerce_currency', function( $currency ) {
      return 'PLN';
   } );

4. Confirm that BLIK and P24 are available as payment options:
5. Go to WC > Settings > Payments > PayPal Checkout > Hide Funding Method(s) and confirm that BLIK is not an option.
6. Check out this branch (issue/796) and see an option for "BLIK" above. Choose to hide the funding method.
7. Refresh the checkout page and confirm that BLIK is no longer an option:

Changelog entry

• Add BLIK and MercadoPago as funding methods

Closes #796.

[chickenn00dle]

LGTM. Merging.