Bring parity feature with classical notebook

[fcollonval]

This PR:

• Moves to the new JupyterLab toolbar definition
• Add button to edit metadata
• Add button to edit attachment and a new attachment tool for the side panel
• Add slideshow selector widget
• Add raw format selector widget
• Add entry menu to hide the toolbar completely
• Add menu in view to toggle some widgets
• Use icons migrated upstreamed to JupyterLab

The menu toggled items apply on the current notebook. If you want to change the default, you need to change the setting.

The toolbar is now a single toolbar. You will need to use a spacer to split elements between left and right sides.

Requirements JLab >=3.4.0

Known limitation:

• Locking tags editor is not available any longer
• The custom view per notebook is not saved in the state (so it won't be restored)