Attempting to pay with a non-available payment method doesn't throw an error.

[senadir]

Related to #5404, when attempting to pay with a payment method that is not available, you don't get an error, the order isn't placed, but is set to pending payment.

Payments can be registered but not available, using a code like this:

add_filter( 'woocommerce_available_payment_gateways', function( $methods ) {
	unset( $methods['cod'] );
	return $methods;
} );

This was protected using get_request_payment_method, but in a recent refactor, that function is no longer called.