Ability to undo changes or revert to a previous version (Versions V2)

## Context

https://cds-snc.freshdesk.com/a/tickets/28813

> Revert a form (while in draft) based on a previously saved copy (instead of uploading an old version as a new form)

https://cds-snc.freshdesk.com/a/tickets/29571

> After publishing a form, and creating a draft v2, how do I delete draft v2? We have no intention of publishing it.

## Current state

There's no way to rollback a form version, can only:
- Revert the changes manually and publish
- Delete the form
- Download the version they wish to keep, delete the current form, recreate the form using the downloaded version
- Currently archive does archive the published form not the draft.

## Form builder needs

- [ ] Undo the latest changes
- [ ] Go back to previous version
- [ ] Delete newly made draft version on a published form
- [ ] Rollback to a specific previous version to replace the current

The issue names no files, tests, or entry points. Start by clarifying which versioning behaviors are required and how drafts, published versions, deletion, undo, and rollback should interact; define acceptance criteria for each requested capability before locating the relevant form-builder code and tests.

Written by the indexing model from the issue text.