Preview of a field formatter settings or custom elements display

Problem/Motivation

To improve a developer experience and speed up development it would be nice to have a preview of API output. The preview could be done on the field/formatter level or the whole ce-display in a similar way that views module provides a preview.

Proposed resolution

There are already methods on the entity to generate fake data, which were added for layout-builder-previews, so that could be used + generate a preview output of an entity.

Remaining tasks

Needs more detailed concept.