feat: Update form builder preview

[timarney]

Summary | Résumé

Updates the form builder preview to add the introduction and policy fields

Example link of existing form

https://forms-staging.cdssandbox.xyz/en/id/25

Longer example:

https://forms-formulaires.alpha.canada.ca/en/id/167

Test instructions | Instructions pour tester la modification

• Create a new form
• Enter content into the introduction and policy locked content areas
• Preview the form

Unresolved questions / Out of scope | Questions non résolues ou hors sujet

👉 This doesn't update the forms core preview. Once the design settles we can handle that part with Core.

Pull Request Checklist

Please complete the following items in the checklist before you request a review:

• Have you completely tested the functionality of change introduced in this PR? Is the PR solving the problem it's meant to solve within the scope of the related issue?
• The PR does not introduce any new issues such as failed tests, console warnings or new bugs.
• If this PR adds a package have you ensured its licensed correctly and does not add additional security issues?
• Is the code clean, readable and maintainable? Is it easy to understand and comprehend.
• Does your code have adequate comprehensible comments? Do new functions have docstrings?
• Have you modified the change log and updated any relevant documentation?
• Is there adequate test coverage? Both unit tests and end-to-end tests where applicable?
• If your PR is touching any UI is it accessible? Have you tested it with a screen reader? Have you tested it with automated testing tools such as axe?

Bonus Unrelated Fix

Updated the element dropdown so it doesn't push the panel open to fit it's content

[github-actions]

Storybooks Link For Branch
https://cds-snc.github.io/platform-forms-client/refs/pull/1060/merge

[pcraig3]

It all works, so I am approving, but I have 2 suggestions (maybe they are for the design team though?)

1. I feel like the "Privacy statement" makes more sense above the confirmation page message because the privacy statement comes first in the actual form preview.
2. Once you are at the bottom of the form, you have to go up again to preview it. Maybe some kind of "preview" button down there, or a floating nav header? (I feel like this one is for the design team to think about.)

[timarney]

It all works, so I am approving, but I have 2 suggestions (maybe they are for the design team though?)

I think this is being iterated on still in Figma so will merge and followup once things settle.