PP-10104 payment page validation bugs

[hjvoid]

WHAT

Fixing payment page form validation bugs which do not work as per current Design system. Also added are a <span> tags with a class of "govuk-visually-hidden" as per GOV.UK Design System.

HOW

1st Bug

1. Go to payment page.
2. Submit an empty form and the page shows the error summary at the top.
3. When you click on each one you should be taken to the corresponding input.

2nd Bug

1. Go to the payment page.
2. Enter an invalid card number in the card number field.
3. The error message should appear after the hint text.

3rd Bug

1. Go to the payment page.
2. Enter the following invalid card number in the card number field: 4444333322221111aaa
3. This should show an error.

4th Bug

1. Go to the payment page
2. Submit an empty form. The page displays the error summary at the top.
3. In the card number field, enter an invalid value and then press tab.
4. The error summary should not be duplicated.

N.B. Will squash on merging.