As a UI user, I want to create and edit content using a Symfony forms based integration

The general idea is to build-up on top of what was added to repository-forms for User Generated Content (EZP-24339), and re-use those elements for content editing in the backoffice as well.

For now, creating content without a draft is the only supported use-case. Other fashions should be added:

• creating content with a draft
• creating a new version of an existing content item
• saving a draft while editing