Revert change to BillingBlock to support hidden fields.

[eileenmcnaughton]

Overview

Partial revert of #12332 per feedback from @mattwire

Before

Some processors would have experienced a regression from #12332

After

Line causing regression removed, field addition handled differently

Technical Details

Per discussion with Matt Wire this is actually unnecessary, if we define 'id' in the payment fields
metadata. This is a bit too much like spooky magic but it ... erm .. works

Comments

We could probably handle adding 'id' in the Payment helper classes. OTOH for most processors just one hidden token field is needed so most processor devs may not hit the need to know to add the id attribute

@mattwire please confirm this is 'good to merge'

[civibot]

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[eileenmcnaughton]

merging to hit rc as this reverses part of a change in the rc

[mattwire]

@eileenmcnaughton Thanks :-)