[DashboardLayout] Show nested navigation in mini-drawer

[apedroferreira]

Initially was just trying to refactor sidebar navigation to use the same navigation cache and utilities as the PageContainer component.

But this required adding nested navigation to the sidebar for consistency with the warnings we show when there are duplicated navigation items, because the navigation links should match in all variants of the sidebar.

TODO:

• Improve tests as mentioned in [DashboardLayout] Support route patterns in navigation #3991 (review)?

Inspiration:

• https://minimals.cc/dashboard

[douglaszaltron]

Nice!

[apedroferreira]

Status: right now with useActivePage there's no way to identify a particular item when its properties are the exact same as another. This would be necessary to identify an item instead of another and show that item only as selected in the sidebar.

If multiple items could be shown as selected simultaneously this would not be an issue, otherwise we need to find a solution. Maybe we could generate item ids every time the navigation is changed, but this could be a bit expensive as we'd have to go through the whole navigation tree.