Implement private types

[Akirathan]

Created from the discussion github.com/orgs/enso-org/discussions/7088

Implement private types. Private type implies that all the fields, constructors, and methods within are private.

Follow-up of #7304

Related to:

• Implement private methods #8834
• Implement private constructors & deconstructors/getters for types #8836

[radeusgd]

This feels redundant. Is this particular feature needed?

It feels like this could be 'emulated' by placing the type inside of a private module (already implemented) + marking its constructors (#8836) and methods (#8834) as private.

[Akirathan]

This feels redundant. Is this particular feature needed?

@radeusgd Good point. Maybe not. Setting the priority to lowest.

[JaroslavTulach]

I assume one can move private type into private module and then it is private. In such case we are don't need this feature urgently.