Backport the preview and test features to original Form component

[dsamojlenko]

Summary | Résumé

This PR backports some customizations we had made to the Form component for use in the Preview and TestDataDelivery functions of the FormBuilder. We had been maintaining a separate copy of the Form component in order to test, but are now backporting those changes, and updating the references to it.

There are three new props on the Form component:

• isPreview (optional | boolean) indicates if this is a Preview and if so, disables the Submit button
• renderSubmit (optional | JSX.Element) if you need to customize around the Submit button (for example, to have a message appear next to it)
• onSuccess (optional | function) on successful submit, fire a provided action, preventing a full redirect (for TestDataDelivery)

Also added the Introduction and PrivacyPolicy RichText components to the form render as well.

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?

[github-actions]

Storybooks Link For Branch
https://cds-snc.github.io/platform-forms-client/refs/pull/1240/merge

[bryan-robitaille]

LGTM