Add a mid-point summary component

[ziggy-cyb]

Is your feature request related to a problem? Please describe.
For lengthy forms it has been indicated by users during testing that they would be worried that the information they have entered may be inaccurate, and this would be especially worrying in cases where certain instructions relayed to the applicant are dependent on their answers in the form.

They have also indicated that one of the features they appreciate about GDS smart answers is the ability to change answers if they've entered them wrong as they go through the form. Although this could pollute the form pages if used for every page, an option whereby the user has certain "checkpoints" where they might want to see their progress so far might be useful.

Describe the solution you'd like

• Repurpose some of the functionality for the repeating field summary page controller to create a new separate component
• This component should allow users to change their answers from earlier in the form, however the user should then have to continue the form from that point, with their answers pre-populated
• This component should only show the questions the user has already answered
• This component should then be available as a content component to any question page

Describe alternatives you've considered

• Repurposing the logic in the SummaryPageController was considered, however due to the complexity in this form around payment, it makes more sense to use the implementation in the repeating field summary instead.
• There was also discussion of allowing summary pages to be added part way through the form, but this would require an overhaul of the current summary page controller, which is a bit OTT for this work

Additional context