Consider replacing MenuItem with Accordion

[javier-godoy]

Nested MenuItems are basically nested Accordions modulo some differences. It would be nice to replace our custom implementation of fc-menuitem with vaadin-accordion (or document what features prevent us from doing so)

[mlopezFC]

I think that fc-menuitem is a better implementation because it allows nested hierarchies and also has a nice animation when opening/closing.
In fact with an empty menu and with this method, it already should be possible to provide an accordion or another component.

[javier-godoy]

I agree.