Add display_builder_entity_form sub-module

Problem/Motivation

It was initially planned for 1.1.0 because we were waiting:

• in Drupal 11.3: 📌 Define form elements from SDC Active
• in UI Patterns 2.x: ✨ Add ui_patterns_field_widgets sub-module Active

However, it seems we don't need to wait. display_builder_entity_view is better with ui_patterns_field_formatters but doesn't need ui_patterns_field_formatters to work.

Proposed resolution

• Add display_builder_entity_form sub-module
• Override Core's EntityFormDisplay class to implement DisplayBuildableInterface
• This implementation will have access to all sources from entity context, so including field formatters, entity links, entity reference... (let's be careful about what is happening when EntityInterface::isNew() === TRUE)
• Add a new Field Widget source, inspired by the field formatter one, only available in this implementation (so with a new context I guess)
• Display the built form instead of the Field UI one. Let's be careful about the admin route/theme condition.