Hidden option for groups and tabs

[daniellienert]

#2118 introduced an inspector option 'hidden' to hide a property from the inspector.

Introduce this option also for groups and tabs.

[Sebobo]

Got a sponsor to implement this, will take care of it 👍

[Sebobo]

I will split this. One part is targeted as bugfix to hide groups & tabs implicitly when all their items are hidden.
The other would be a feature to hide groups & tabs explicitly via the mentioned option.