closes #72982

What and Why?

Adds a new lazy-editor package to improve the loading performance of the editor. It's kind of experimental for now and only used in the boot package to support rendering the selected post in the canvas. Let's prove it in this separate context and bring it later to the site editor (might require some BC / fallback handling)

How?

New Packages:

• @wordpress/asset-loader: Utility for dynamically loading WordPress scripts/styles with dependency resolution
• @wordpress/lazy-editor: Lazy-loading editor component with automatic asset and settings management

Boot Package Changes:

• Added canvas surface as a third surface (alongside stage and inspector)
• Canvas component dynamically imports lazy-editor to avoid bundle bloat
• Routes can export a canvas() function to specify what to render
• Post-list route shows canvas preview when in list view layout
• Add Assets endpoint to the editor endpoint controller.
• Canvas always renders in preview mode for now, will expand later with full screen mode.(read-only, no toolbars)

Testing Instructions

1. Navigate to the boot's post list route http://localhost:8888/wp-admin/admin.php?page=gutenberg-boot&p=%2Ftypes%2Fpost%2Flist%2Fall
2. If the view is in list layout, you should see:
   • Post list on the left (stage surface)
   • Post preview on the right (canvas surface)
3. The preview should be read-only with no editor toolbars visible